This article examines the ideas on the origin of the name Rus (Russian: русь) formulated by Gottlieb Siegfried Bayer (1694–1738), a professor at the St Petersburg Academy of Sciences. Bayer expressed his observations in an unfinished Latin text published after his death in the journal of the Academy. Using this publication, which has never been translated into Russian, the authors of the article examine Bayer’s critical comments and objections to various versions of the origin of the name Rus. Bayer’s text is a kind of catalogue of hypotheses that existed in the academic world in the first half of the eighteenth century. From the point of view of modern scholarship, all of them can be regarded as naive folk etymologies or legends (for example, the creation of the name Rus from the ancient name of a river, its comparison with the biblical people of Rosch, or the appeal to the legend of the brothers Lech, Czech and Rus, etc.). These versions are subjected to a fair and ironic criticism by Bayer. Based on new research on ideas of ethnic nomination, the authors place the versions in the context of discussions in historical writings of the sixteenth–eighteenth centuries. The results of the analysis of Bayer’s arguments show that he often makes very good use of his knowledge of ancient and modern languages and of the historical context to criticise other people’s versions. The article also examines in detail the etymology to which Bayer himself adheres. According to Bayer, the name of the Russian people comes from the Slavic word рассеяние (“dispersion”). This etymology was proposed in the sixteenth century by the Austrian diplomat Siegmund von Herberstein and supported by some Polish and German scholars. The authors show that Bayer finds additional historical and linguistic arguments for this hypothesis, which, of course, do not withstand the criticism of contemporary scholarship. The article notes the influence of Bayer’s hypothesis on the ideas of G. F. Mьller. The authors suppose that a certain forgetfulness of Bayer’s hypothesis is due to the fact that it contradicts his reputation as a “Normanist”.