'adieu' originates from Old French, specifically the phrase 'a Dieu,' where 'a' meant 'to' and 'Dieu' meant 'God.'

'a Dieu' transformed into the Middle English word 'adieu,' and eventually became the modern English word 'adieu.'

Initially, it meant 'to God,' as in a farewell blessing, but over time it evolved into its current meaning of 'goodbye.'