'stew' originates from Old French, specifically the word 'estuve'/'estuver' meaning a heated bath or to heat, where the stem 'estu-' referred to heat or a heated place.

'stew' changed from Middle English forms borrowed from Old French 'estuve'/'estuver' and eventually became the modern English word 'stew', which broadened from 'heated place/bath' to cooking and figurative senses.

Initially, it referred to a 'hot bath' or 'heated place'; over time it evolved into meanings related to 'heating' as in cooking slowly in liquid and, by metaphorical extension, a state of agitation or worry.