'apostatize' originates from Greek, specifically the word 'apostasia' (ἀποστασία), where the prefix 'apo-' meant 'away from' and 'stasis' (related element) meant 'a standing' or 'standing apart'.

'apostatize' changed from Late Latin/Medieval Latin 'apostatizare' (via Medieval Latin formations based on Greek) and eventually entered modern English as 'apostatize' (with verb-forming suffix -ize).

Initially it meant 'to revolt or defect (from allegiance)' in the sense of physical or political defection; over time it came to be used especially for 'renouncing a religious faith or belief', the sense that predominates in modern usage.