'backtrail' originates from Modern English as a compound of 'back' + 'trail'. 'back' comes from Old English 'bæc' meaning 'back' or 'behind', and 'trail' ultimately derives from Latin 'trahere' (via Old French/Anglo-French forms meaning 'to pull' or 'to draw'), producing meanings related to a beaten path or track.

'backtrail' was formed in Modern English by compounding the words 'back' and 'trail'. The element 'back' evolved from Old English 'bæc' with a stable meaning of 'rear/behind', while 'trail' developed from Latin 'trahere' through Old French (e.g. 'trailer'/'trailler') and Middle English ('trailen'/'traillen') into the sense of a dragged path or track; these combined to give the compound sense.

As a compound, 'backtrail' has essentially taken the literal combined meaning of its parts—'a trail for going back' or 'to go back along a trail'—and has retained that basic sense in modern usage.