'backblow' originates from English, specifically a compound of the words 'back' + 'blow'.

'back' derives from Old English 'bæc' meaning 'rear, backward', and 'blow' derives from Old English 'blāwan' (to blow) / related sense 'to strike'; these elements were combined in Modern English to form the compound 'backblow'.

Initially it could refer simply to a blow struck from the rear or a backward-directed blow, but over time it has been used to mean a retaliatory or counter blow returned against an attacker.