'backstay' originates from English, specifically a compound of 'back' and 'stay', where 'back' meant 'rear' and 'stay' meant 'a rope or support used to steady a mast or structure.'

'stay' entered Middle English from Old French 'estai' (support), ultimately from Latin roots related to 'stare' (to stand). The compound 'backstay' developed in nautical English to denote the stay running aft, becoming established in the 18th–19th century nautical vocabulary.

Initially it referred specifically to a stay running to the back (stern) of a vessel; this core meaning has been retained, with occasional extension to any rearward supporting stay or the action of using such a stay.