The name ''Bulgaria'' is derived from the ''Bulgars'', a tribe of Turkic origin that founded the First Bulgarian Empire. Their name is not completely understood and is difficult to trace back earlier than the 4th century AD, but it is possibly derived from the Proto-Turkic word ''bulģha'' ("to mix", "shake", "stir") and its derivative ''bulgak'' ("revolt", "disorder"). The meaning may be further extended to "rebel", "incite" or "produce a state of disorder", and so, in the derivative, the "disturbers". Tribal groups in Inner Asia with phonologically close names were frequently described in similar terms, as the Buluoji, a component of the "Five Barbarian" groups, which during the 4th century were portrayed as both: a "mixed race" and "troublemakers".