'aqueous' originates from Latin, specifically the word 'aqueus', where 'aqua' meant 'water'.

'aqueous' changed from the Late Latin word 'aquosus' (from 'aqueus') and eventually became the modern English word 'aqueous' via Medieval/Latin borrowings into English.

Initially, it meant 'of or pertaining to water'; over time it retained that core sense and came to be used especially in chemistry to describe water-based solutions and water-like properties.