From earlier *bojan- (compare Ancient Greek βοάνος (boános), attested in the 10th century), a borrowing from a Turkic language, probably from Avar bajan (“ruler of the horde”), the title of the Avars' khagan misinterpreted as a name (compare similar development in *vodzь), from Proto-Turkic *bāj (“rich, noble”). The Turkic word is usually considered a borrowing from an Iranian language, from the same lexical root whence also Proto-Slavic *bogъ (“god”), but some consider it inherited from Proto-Altaic.
- *banьjь (“of or pertaining to a ban”)
- South Slavic:
- Gluhak, Alemko (1993) Hrvatski etimološki rječnik (in Serbo-Croatian), Zagreb: August Cesarec, page 123f
- Skok, Petar (1971) Etimologijski rječnik hrvatskoga ili srpskoga jezika (in Serbo-Croatian), volume I, Zagreb: JAZU, page 104
- Starostin, Sergei; Dybo, Anna; Mudrak, Oleg (2003), “*bēǯu”, in Etymological dictionary of the Altaic languages (Handbuch der Orientalistik; VIII.8), Leiden, New York, Köln: E.J. Brill