Place names of an era of the Old Russian state, being a cultural heritage of ethnic community of east Slavs, store in itself memory of the past of the Slavic people and their representations of a world order. As geographical names differ known stability and conservatism, the perspective of their studying is on a joint of history of language, etymology, lexicology and dialectology. Indirectly reflecting historical and geographical reality, geographical names the XI–XIII centuries keep forever sociocultural, historical, lexicological and ethno geographical information, reflect valuable data on language contacts and ancient ethnic communications, migrations of the people, culture, a life and their language consciousness. Certificates of written monuments are defined by that value, «which helps to add our idea of toponymic system on any synchronous cut, about structure of loans, their shifts and rates of adaptation, about the contacting native toponymy going back to unwritten languages and being one of the major sources of data on language of the before Russian population» [4, t. 2, р. 31].
Value of data of a hydronimiya within studying of history, language and culture of ethnos is difficult for overestimating, as water objects at an early stage of development of any civilization had paramount value. In particular, exactly along the rivers there was a moving of certain ethnic groups.
Hydronyms (proper names of a body of water), the writings fixed in Old Russian monuments, including in «The Song of Igor’s Campaign», owing to known stability allow to reconstruct the ethno linguistic map of the past of the East Slavic people. The multilayered objects of hydrography within a certain territory testifying to their various languages possessive, and also about processes of migrations.
«The Song of Igor’s Campaign» reached us in the list of the end of XV – the beginnings of the XVI centuries which was in library of a Spaso-Yaroslavsky monastery, and then was acquired by count A.I. Musin-Pushkin. This list is remote from the original about three centuries (1185–1190). In the Ipatyevsky annalistic list the story about Igor’s campaign «is placed in the text of the Kiev chronicle which, in turn, got data from chronicles of Chernigov» [7, р. 92–93]. Igor Svyatoslavich’s entering into the Lavrentyevsky chronicle the history, appeared in it taken of chronicles of Suzdal, and was transferred to the local chronicle of Pereyaslavl Southern.
As G.F. Kovalev notes, «from the point of view of proper name theory this work gives in hands of the researcher excellent, often a unique material. These are personal names of heroes of the poem, the name of the ancient cities, settlements, the rivers, the names relating to ancient Slavic mythology» [5, р. 48].
The toponymic space of the text develops of place names (117 units), relating on the origin to different languages and fixed in different territories. It in the majority geographical names, going back to lexicon of Slavic, Turkic, Norman and Finno-Ugric languages. «For the most ancient geographical names, especially with the indefinite inner form, only belonging to a family of languages usually is defined. For structural and semantic clear geographical names reference to group of related languages is possible…» [2, р. 192].
The most ancient layer of toponymic lexicon make hydronyms – own names of any object of hydrography: the seas, the rivers, lakes, a well, a reservoir, suited, etc.  – which can be divided on names of the seas (and also sea water areas: lip, gulf, bay), names of the rivers, names of lakes (and also ponds), names of bogs (boggy places), microhydronyms (names of sources, streams, springs, wells, etc.).
In «The Song of Igor’s Campaign» the following objects of hydrography are fixed:
Names of the seas
Pomorie (the coast of the Sea of Azov, the earth on Sula’s right river bank, bordering on the polovetsky steppe): «Div is aroused, he shrieks a command to the unknown land, to the Volga, Pomorie, Posulie, Surozh...» [10, fr. 29]. Geographical name with konfiks: a prefix on- + a nominal basis + a suffix –jе: Po-mor’-je.
Names of the rivers
Bolonie (in English translation thickets) (the low bank of Dniepr where the Kiev Podol settled down): «In the thickets at Plesensk there were four brother princes, and they were carrying me toward the dark blue sea» [10, fr. 99]. N.V. Charlemagne believes that it is a space between shaft – protective constructions on both parties of the bottom watercourse of Glubochitsa, i.e. in close proximity to Kiev; this place was called subsequently as Obolon’ [9, t. 1, р. 134]. Bolonie is «a water meadow, the lowland». According to F.F. Fortunatov, it is connected about a bog, lit. baltas «white», also lit. balnas «white» [3, t. 1, р. 189].
Volga (the largest river of the Russian Plain) is repeatedly mentioned in the text hydronym. «In the second floor XII century within Old Russia (generally – the Vladimiro-Suzdalsky principality) there were headwaters of Volga, approximately to a place of a confluence in it of Sura and Vetluga. Below on the Volga Current settled down the earth of the Volga Bulgarians» [9, t. 1, р. 223]. «For you can empty the Volga with oars; You pour out the Don with your helmet» [10, fr. 124] (Here the mention of Volga is connected with Vsevolod Big Nest’s war with Bulgarians.); «Div is aroused, he shrieks a command to the unknown land, to the Volga, Pomorie, Posulie, Surozh and Korsun» [10, fr. 29] (In the specified context means the average and the bottom Volga Current where there lived the steppe people.). The origin of the name is disputable. «Existence of the rivers of Volgayoka, Vol’ga (Volga), Volgoma, Volgozero’s lake in space from Oka to Karelia allows to assume name emergence Volga in language of the tribes which living in its headwaters at the time of a neolith and have extended later on more northern areas. But sources and the headwaters of the river are in a zone where prior to the beginning of II thousand lived the Baltic tribes. In balt. valka languages «small stream; a stream flowing on a bog; small river, spring»; this term is often compared with the name Volga, i.e. the Neolithic population of a wood zone could be Indo-European. Some authors allow origin Volga from an ancient word, related slav. moisture, volgly; this etymology causes objections, and, besides, it is improbable that this large river before arrival of Slavs remained anonymous» [8, р. 102].
The name Dvina (runs into the Dvina Bay of the White sea) mentions in a context: «The Dvina flows like a swamp for those awesome men of Polotsk» [10, fr. 143] (Here the mention of Dvina indicates narration transition from southeast border of Russia to northwest, to Polotsk princes). «In Russian chronicles it is mentioned as Dvina; the Velikoustyuzhsky chronicle contains an explanation: «Dvina therefore called that moved two (the rivers, – the Yug and Sukhona) and made from itself the third»: this explanation then repeated up to the Encyclopedic dictionary of 1901, but is recognized naive later . Possibly, emergence of the name Dvina (from the middle of the XIX century Northern Dvina) it is necessary to consider in connection with all hydronyms from a basis dvin- which have quite extensive area» [8, р. 374]. Considering that names of Dvina Western and Dvina Northern are conformable in Slavic, Finnish, the Scandinavian languages and at the same time are separated from the Latvian-Lithuanian name, V.A. Bulkin established the phenomenon to «a mirror hydronimiya» when both rivers, in this case both Dvina appears are geographically compatible. «The rivers with the same name with the pulled together sources and dispersing courses served, according to the researcher, certain reference points on portage sites upon transition from the basin of one river to the pool another. Fixing of the name of the river at men of Polotsk was promoted clear to Slavs by semantic contents of the term reflecting local geographical feature – merge at Polotsk two rivers realized as means of communication» [9, t. 2, р. 86–87]. «It is possible, it is more ancient i.-e. the name which by Y. Rozvadovsky carries to other – Old Indian dhavate, dh?vati «flows», dhautis «a spring, a stream» [3, t. 1, р. 488].
Dniepr Slovutich (modern Dniepr, the river running into the Black Sea): «O Dniepr, Son of Fame!» [10, fr. 178]. Dniepr – «the river moistening, impregnating the earth». From *Dunipros > *Duneapar > ; slav. *Dъneprъ > Old Russian Дьнепрь, 1016; Дънепръ, 1214 [8, р. 142]. Concerning an epithet «Slovutich» V.P. Adrianova-Peretts noted that «existence in the Ipatyevsky chronicle under 1241 of a word «slovutny» with the same significance «nice, well-known» – «slovutny the singer Mitusa» – enters also definition «Slovutich» into lexicon modern to language «The Song...». In its basis widespread verb from the most ancient monuments «слути, слову», one of which meaning «to be known, glorified» [9, t. 2, р. 124].
Donets (Severski Donets, right inflow of Don): «but Prince Igor had dashed like an erinine to the weeds... and he sped toward the bend of the Donets» [10, fr. 188, 190]. Judging by numerous researches, in Old Russia the Severski Donets was called as Don (for the first time the specified opinion was stated by V.N. Tatischev, B.A. Rybakov subsequently is proved), and Donets or Little Donets, probably, called Udy river. Despite a community of the main geographical reference points, Old Russian authors could have various systems of geographical representations. In this name Donets – diminutive from Don (Great Don), formed by means of a suffix – ets.
Donets Little: «Igor... measures the steppe in his thought from the great Don to the little Donets» [10, fr. 185] (Small Donets is Udy river, the right inflow of the Severski Donets here is probably called).
Don (the river running into the Sea of Azov): «Igor is leading his warriors to the Don» [10, fr. 30]. The name is given by the Iranian people that are once living in the territory of Northern Black Sea Coast. In their language don is «river» [8, 144].
Don Great: «The Polovtsians, by uncharted routes, raced toward the great Don» [10, fr. 30] (In this context it means the average watercourse Donets, because Igor’s fight occurred to Polovtsians to the west of the Severski Donets). Big geographical objects are, as a rule, richer with resources necessary for life and consequently are allocated as reference points. In toponymic forms adjective «great» matters «big». Opposition of toponyms with adjective components «great» – «small» very frequent phenomenon, including in a hydronimiya. The dichotomy «great-small» could have in the ancient time geographical meaning «northern-southern». So, the northern cities called «great», and southern – «small».
Danube: «Maidens sing on the Danube; their voices are heard across the sea in Kiev» [10, fr. 212] (the poetic name of the river in general here is meant). Celtic by origin the Danuv form «indicates communication of it hydronym about Iran. danu «river» [8, 147]. In chronicles the geographical name is mentioned from X-th century.
Kaiala (the symbolical or place name of the river on which there was Igor’s fight to Polovtsians in 1185): «There the brothers were parted on the banks of the swift Kaiala» [10, fr. 71]. The origin of hydronym is disputable. Especially in detail the origin of geographical name Kaiala from a Old Russian verb «каяти» was proved by L.A. Dmitriev who came to a conclusion that Kaiala – a common noun, instead of proper which was given by the author of «The Song…» to «the river carrying any other place name» [9, t. 3, р. 33]. M. Fasmer two options of etymology were offered: from the Turkic kaja – «the rock»; from the Turkic kajan – «a fast, mountain stream, falls» [3, t. 2, р. 216]. According to N.A. Baskakov, the etymology of the name of the river «can be opened under condition of the accounting of other name either the same river, or another, mentioned in Russian chronicles in connection with Igor Severskyi’s campaign, namely the rivers Syuurlyi» [1, р. 243]. The researcher frames a number of hypotheses about an origin of hidronym, making the name from the following Turkic words: qo?aly, qyjaqly – «abounding with sedge»; qyjyly – «with a narrow strip of the coast between rocks and the river»; qyjyqly – «twisting, with bends». Anyway, supporters of a Turkic origin correlate Kaiala’s name to real geographical objects, and supporters of Russian etymology consider Kaiala by the symbolical river.
Nemiga (the small river near modern Minsk, inflow of Svisloch): «opened the gates of Novgorod, smashed the glory of Iaroslav and as a wolf leapt to the Nemiga» [10, fr. 156, р. 157]. The first publishers of «The Song…» (including N.M. Karamzin), identified Nemiga with Neman, being guided by V.N. Tatischev’s opinion. «But in 1821 of Z.D. Hodakovsky in hand-written «The historical and geographical dictionary» identified Nemiga with a channel in Minsk, and N.P. Barsov wrote that «a stream Nemiga and exists hitherto in Minsk, its bloody coasts are mentioned by the «The Song of Igor’s Campaign» which author certainly knew about bloody defeat of Minsk by Monomakh» [9, t. 3, р. 310].
Posulie (left coast of Dniepr): «Div is aroused, he shrieks a command to the unknown land, to the Volga, Pomorie, Posulie» [10, fr. 29]. The geographical name from Sula with konfiks: a prefix on- + a nominal basis + a suffix – jе: Po-sul’-je.
Ros (the right inflow of Dniepr running into it to the south of Kiev; the river, boundary with the polovetsky steppe): «Along the Ros and the Sula pagans are portioning the cities» [10, fr. 137]. Possibly, the proper name is related to the word «course» [3, t. 3, р. 506].
Stugna (the right inflow of Dniepr running into it of 30 km below Kiev): «Not such was the River Stugna, having a poor current… At its dark banks as the Dnieper it closed over young prince Rostislav» [10, fr. 197] (River Stugna at that time unexpectedly spread; prince Rostislav Vsevolodovich sunk in it). The name is connected with Old Russian verb стугнуть «to run cold» [3, t. 3, р. 786]. On Stugna’s left (northern) coast the cities of the main defensive line of Russia on border with the Steppe settled down [9, t. 5, р. 76].
Sula (the left inflow of Dniepr running into it to the south of Kiev behind which the polovetsky steppe began): «Now the silvery current of the Sula no longer flows to the city of Pereiaslavl...» [10, fr. 143]. Name, possibly, primordial-Slavic. Сompare got.bi-sauljan «to soil, pollute», Norw. soyla «silt, bog», Swed. saula «dirt» [3, t. 3, р. 800]. According to N.A. Baskakov, the proper name Sula «suwlaq – suwla? would be characteristic for the settlement, than for the river name rather, the last could occur from other derivative form suw «water», namely from suw-ly «having water, with water, full-flowing», i.e. from suw «water» basis + a possession affix –ly > suw-ly > Russian Sula» [1, р. 110].
Kanin (a stream near to Chernigov, mentioned also in the Lavrentyevsky chronicle): «Pride brought Boris Viacheslavich to judgment on the River Kanina Pride spread a green shroud for the brave and young prince, to the disgrace of Oleg» [10, fr. 47]. Group of researchers (F. Timkovsky, I. Snegiryov, M.A. Maksimovich, etc.), considered Kanin as a proper name, connecting this word with the name of the district being near to Chernigov and mentioned under 1152 in the chronicle. «The Bulgarian scientists N.M. Dylevsky and B.S. Angelov represented in the articles data about existence on the Balkans the river «Kanina» and the city with the same name» [9, t. 4, р. 10]. In this geographical name kanin – a possesive adjective from Russian nickname Каня (a bird каня, канюк «buzzard») [8, р. 186].
Names of water objects are a valuable historical and linguistic source as rather seldom change for the extra linguistic reasons, remaining throughout many centuries. Besides, in some cases hydronyms promote restoration of personal own names and the nicknames which have not been fixed by historical sources. Such personal names and nicknames can be discovered and in structure of names of the cities. Names of water objects find close interrelation both with names of the cities and with others hydronyms. For example: Don River and its inflow Severski Donets; river Sula and Posulie  and under.
Within historical toponymics very important there is a question of motives of motivation of geographical names. In «The Song of Igor’s Campaign» the group of the landscape place names, indicates the sizes and a configuration of natural objects, features of a hydrology and a relief, flora and fauna. In the Old Russian monument are fixed the names having as a motivation basis a proper name of the person, connected with called object on the birth, an occupation and the possessive relations. A group of geographical objects connect with the color characteristic in the toponymic nomination, an ethnic origin, communication with Christian faith and divine service.