'backstroke' originates from English as a compound of 'back' and 'stroke'. 'back' comes from Old English 'bæc' meaning 'the rear part of the body or behind', and 'stroke' comes from Old English 'strāc/strac' meaning 'a blow, movement, or stroke'.

'backstroke' developed from the two-word phrase 'back stroke' used in earlier Modern English descriptions of swimming and later fused into the single word 'backstroke' in modern usage.

Initially it simply described a 'stroke done on the back'; over time it became the standardized name for the specific swimming style and race stroke called the backstroke.