'castigator' originates from Latin, specifically the word 'castigātor', where the verb 'castigare' meant 'to chastise or correct' (ultimately from 'castus' meaning 'pure' and a form related to 'agere' meaning 'to drive/lead').

'castigator' changed from medieval Latin 'castigātor' and was influenced by Old French forms such as 'castigateur', and eventually entered English as the modern word 'castigator' via Middle English/early modern usage.

Initially, it meant 'one who chastises or corrects (often with a notion of purifying)', but over time it evolved into the current sense of 'one who severely criticizes or punishes'.