The book examines the names of Lake Baikal that were used by different peoples - Lamu, Beihai, Tengis, Dalai, Baigal, Baikal, etc. The most mysterious of them is Baigal (Baikal). To explain its origin, various options have been proposed - Chinese, Dinlino-Ket, ancient Turkic, Buryat, Yakut, Arabic, Tibetan. The most probable are Buryat and Yakut, in which the search for the origins of the word “Baigal” is underway. The linguistic affiliation of words, myths, legends, songs of the Buryats and Yakuts, their heroic epics, history and ethnogenesis, as well as anthropology are considered. The first edition (1982) was published under the same title. For a wide range of readers interested in the history of our Motherland.