'drainage' originates from Old French, specifically the word 'drenage', where 'dren-' meant 'to draw off liquid'.

'drenage' transformed into the Middle English word 'drainage', and eventually became the modern English word 'drainage'.

Initially, it meant 'the act of drawing off liquid', but over time it evolved into its current meaning of 'the process or system by which water or other liquids are drained from an area'.