'autobus' originates from French, specifically the word 'autobus,' formed from the prefix 'auto-' (from Greek 'autos,' meaning 'self') and 'bus' (shortened from Latin 'omnibus').

'autobus' entered English in the late 19th century from French 'autobus'; the shorter form 'bus' (from 'omnibus') became the dominant English form later.

Initially it meant 'a self-propelled omnibus' (a motor omnibus); over time the shorter form 'bus' became the common term and 'autobus' grew rare or seen as borrowed/archaic.