Najib Hamadani and Ahmed at-Tusi’s Bulgarian oikonyms and their location in the former Volga Bulgaria

This article attempts to localize the fortresses of the Volga Bulgars (first of all, fortresses Marj and Tehshu) known from medieval authors reportedly Najib Hamadani and Ahmed at-Tusi. In the course of solving this problem the question of these authors data reliability is raised, as well as the common source of this information borrowing. There is a good reason to see this in the source known among the Arab-Persian historical and geographical medieval manuscripts as Rizal by Ahmed ibn Fadlan, the Secretary of Abbasid embassy to the Volga Bulgars Elteber Almush, who visited the Volga in 922. This fact explains the absence of Bulgarian cities known from other sources in the given lists as well as the question of uniqueness of Hamadani and at-Tusis information. On the basis of the sources synthesis, place-and folklore studies, the article proposes some options for localization of some of these forts and etymology options of Bulgarian oikonyms mentioned in the papers by the considered authors. The author proves the importance of place names data at the present stage of Bulgar study research, especially of Volga Bulgaria historical geography as well as further studies are planned.