'estuary' originates from Latin, specifically the word 'aestuarium,' where 'aestuare' meant 'to boil or surge.'

'aestuarium' transformed into the Old French word 'estuaire,' and eventually became the modern English word 'estuary' through Middle English.

Initially, it meant 'a place where water boils or surges,' but over time it evolved into its current meaning of 'a tidal mouth of a large river.'