Galla was an outsider’s label for Oromo people. [fact]
The name Galla, which is of obscure origin, is first recorded in the sixteenth century: it is used without always a specific ethnic connotation in Ethiopia to designate traditionally 'subject' peoples. The Galla call themselves Oromo.
I.M. Lewis, I. M. Lewis, A Modern History of the Som…, loc. 735