J. B. Bury derived the title from the name of Avar khagan Bayan I, and Bulgarian khagan Kubrat's son Batbayan, with which tried to prove the Bulgarian-Avar (Turkic) theory on the origin of early medieval Croats. Historian Franjo Rački didn't discard the possibility South Slavs could obtain it from Avars, but he disbelieved it had happened in Dalmatia, yet somewhere in Pannonia, and noticed the existence of "bân" ("dux, custos") in Persian language. Tadija Smičiklas and Vatroslav Jagić thought that the title should not derive from "bajan", but from "bojan", as thus how it is written in the Greek historical records ("boan", "boean").