'chastise' originates from Middle French, specifically the word 'chastier', which in turn comes from Latin 'castigare' where 'castigare' meant 'to correct' and is related to 'castus' meaning 'pure'.

'chastise' changed from the Middle French word 'chastier' (and Old French forms) and entered Middle English as forms like 'chastisen' before becoming the modern English 'chastise'.

Initially, it meant 'to make pure or correct' (in a moral or disciplinary sense), but over time it evolved into the current primary sense of 'to reprimand or punish to correct behavior'.