'purgative' originates from Latin, specifically the word 'purgativus', where 'purgare' meant 'to cleanse' (from 'purus' meaning 'pure').

'purgative' changed from Latin 'purgativus' through Medieval Latin/Old French forms (e.g. Middle French/Anglo-French 'purgatif') and eventually became the modern English word 'purgative'.

Initially, it meant 'causing cleansing' in a general sense; over time it came to be used especially for substances that cleanse the bowels, i.e., 'medicine that causes evacuation of the bowels', while retaining a figurative sense of moral or ritual cleansing.