'back-to-front' is a compound of the words 'back', 'to' and 'front'. 'back' originates from Old English 'bæc' meaning 'the rear part of the body, back'; 'to' is from Old English 'to' (a preposition indicating direction); 'front' originates from Old French 'front', from Latin 'frons' meaning 'forehead' or 'fore part'.

The phrase derives from the literal spatial sense 'from the back toward the front' in earlier English; over time the assembled phrase 'back to front' (often hyphenated when used adjectivally) was used to describe items with front and back reversed and then extended figuratively to mean things arranged incorrectly or in reverse order.

Initially it described physical orientation ('from back toward front'); over time it developed the broader meaning 'reversed or in the wrong order', which is the common modern sense.