The origin of the name is a matter of considerable dispute. In general, the hypothesis of E. Kunik and Vilhelm Thomsen has met with the widest acceptance. According to them this appellation derives from the Finnic languages. The name of Sweden in Finnish is Ruotsi; in Estonian: Rootsi. This name is commonly held to be derived from Roslagen, the coastal areas of the Uppland province in Sweden. The Danish scholar T.E. Karsten has pointed out that the territory now occupying the areas of Uppland, Sodermanland and East Gotland in ancient times was known as Rođer or rođin. Thomsen accordingly has suggested that Rođer probably derived from rođsmenn or rođskarlar, meaning seafarers or rowers.
However, it has been also suggested that the name Rus might have originated from the Iranic name of the Volga River (by F.Knauer Moscow 1901), as well as from the Rosh of Ezekiel. Prof. George Vernadsky has suggested a derivation from the Roxolani or from the Aryan term ronsa (moisture, water). There is a recurrence of river names like Ros in Eastern Europe.
Later, the Primary Chronicle tells us, they conquered Kiev and created the state of Kievan Rus' (which, as most historians agree, was preceded by the Rus' Khaganate). The territory they conquered was named after them as were, eventually, the local people (see Etymology of Rus and derivatives for further details).
Apart from Ibn Fadlan's account, the Normanist theory draws heavily on the evidence of the Persian traveler Ibn Rustah who allegedly visited Novgorod (or Tmutarakan, according to George Vernadsky) and described how the Rus' exploited the Slavs.
In his treatise De Administrando Imperio, Constantine VII describes the Rhos as the neighbours of Pechenegs who buy from the latter cows, horses, and sheep "because none of these animals may be found in Rhosia". His description represents the Rus as a warlike northern tribe. Constantine also enumerates the names of the Dnieper cataracts in both Rhos and in Slavic languages. The Rhos names have distinct Germanic etymology:
The proponents of this theory claim that the name Rus, like the Finnish name for Sweden, is derived from an Old Norse term for "the men who row" (rods-) as rowing was the main method of navigating the Russian rivers, and that it is linked to the Swedish coastal area of Roslagen (Rus-law) or Roden, from where the Varangians came from according to the Russian Primary Chronicle. The name Rus would then have the same origin as the Finnish and Estonian names for Sweden: Ruotsi and Rootsi.
It has been suggested that the Vikings had some enduring influence in Rus, as testified by loan words, such as yabeda "complaining person" (from aembaetti "office"), skot "cattle" (from skattr "tax") and knout (from knutr, "a knotty wood"). Moreover three Nordic names of the first Varangian rulers also became popular among the later Rurikids and then among the East Slavic people in general: Oleg (Helgi), Olga (Helga) and Igor (Ingvar).
The Normanist theory was first elaborated by the German historian Gerhardt Friedrich Müller (1705-1783), who was invited to work in the Russian Academy of Sciences in 1748. At the beginning of his notorious speech from 1749, Müller declared that the "glorious Scandinavians conquered all the Russian lands with their victorious arms". As the rest of the speech represented a lengthy list of Russian defeats by the Germans and Swedes, Müller was forced to curtail his lecture by shouts from the audience. The scathing criticism from Lomonosov, Krasheninnikov, and other academicians led to Müller being forced to suspend his work on the issue until Lomonosov's death. Although the printed text of the original lecture was destroyed, Müller managed to rework it and had it reprinted as Origines Rossicae in 1768.
Other notable proponents of the "Normanist theory" of the Russian state — including Nikolai Karamzin (1766–1826) and his disciple Mikhail Pogodin (1800–75) — gave credit to the claims of the Primary Chronicle that the Varangians were invited by East Slavs to rule over them and bring order. The theory was not without political implications. In Karamzin's writing the Normanist theory formed the basis and justification for Russian autocracy (as opposed to anarchy of the pre-Rurikid period), and Pogodin used the theory to advance his view that Russia was immune to social upheavals and revolutions, because the Russian state originated from a voluntary treaty between the people of Novgorod and Varangian rulers.
The staunchest advocate of the anti-Normanist views in the post-WWII period was Boris Rybakov, who argued that the cultural level of the Varangians could not have warranted an invitation from the culturally advanced Slavs. This conclusion leads Slavicists to deny or reinterpret the Primary Chronicle, which claims that the Varangian Rus' were "invited". Rybakov assumes that Nestor, putative author of the Chronicle, was biased against the pro-Greek party of Vladimir Monomakh and supported the pro-Scandinavian party of the ruling prince Svyatopolk. He cites Nestor's factual inaccuracies as pro-Scandinavian manipulations and compares his account of Rurik's invitation with numerous similar stories found in folklore around the world.
Quite a few alternative, non-Normanist origins for the word Rus have been postulated by Sigismund von Herberstein, Ilovaisky, Rybakov, and others, although none was endorsed in the academic mainstream:
According to F. Donald Logan (The Vikings in History, cit. Montgomery, p. 24), "in 839, the Rus' were Swedes. In 1043, the Rus' were Slavs." The Scandinavians were completely absorbed and, unlike their brethren in England and in Normandy, they left little cultural heritage in Eastern Europe. This almost complete absence of cultural traces (besides several names, as discussed above, and arguably the veche-system of Novgorod, comparable to thing in Scandinavia), is remarkable, and the Slavicists therefore call the Vikings "cultural chameleons", who came, ruled and then disappeared, leaving little cultural trace in Eastern Europe. This seems to suggest that these Rus' were a small group, less than a people in the nation sense of the word; less than an ethnos.