'backrush' originates from English, specifically a compound of 'back' and 'rush', where 'back' meant 'rear' or 'in the opposite direction' and 'rush' meant 'to move quickly or surge'.

'backrush' developed in Modern English as a compound (from the element 'rush' + 'back' or the phrase 'rush back'), reflecting the notion of a rush in the backward direction; similar expressions like 'rush back' appear in earlier English usage.

Initially it simply described the action of 'rushing back' (a movement toward the rear); over time it has been used as a noun to describe a single event or occurrence of such a backward surge, especially of water.