'apostatise' originates from Greek via Late Latin, specifically the Greek noun 'apostasia' (ἀποστασία), where the prefix 'apo-' meant 'away' and 'stasis' (στάσις) meant 'a standing' or 'a standing off'.

'apostatise' entered English through Late Latin 'apostasia' and Middle English forms such as 'apostasie' (from Old French), and eventually developed into the modern English verb 'apostatise' (and the related noun 'apostasy').

Initially it referred literally to 'a standing away' or 'defection'; over time it came to mean specifically the act of abandoning or renouncing a previously held religious, political, or ideological belief.