'atabeg' originates from Turkic, specifically the elements 'ata' + 'beg', where 'ata' meant 'father' and 'beg' (also spelled 'bey') meant 'lord' or 'chief'.

'atabeg' passed into Persian and Arabic as forms such as 'atābak' / 'atābeg' and was used in medieval sources; the term entered European historiography and eventually became the modern English 'atabeg'.

Initially it carried the literal sense of 'father-lord' or guardian of a prince; over time it came to denote both the guardian/regent role and, in many cases, a hereditary regional ruler.