'assuage' originates from Old French, specifically the word 'assouagier', where the root goes back to Late Latin 'assuaviare' (from Latin 'ad-' + 'suavis'). 'ad-' meant 'to/toward' and 'suavis' meant 'sweet, pleasant'.

'assuage' changed from Old French 'assouagier' into Middle English forms (such as 'asswage') and eventually became the modern English word 'assuage' (and its derivatives like 'assuaged').

Initially, it meant 'to make sweet or soften', but over time it evolved into the current meanings of 'to make less intense, to soothe or relieve' and 'to satisfy or appease'.