'backup' originates from English, specifically the compound of 'back' + 'up', where 'back' meant 'the rear' and 'up' meant 'toward a higher position or direction'.

'back' comes from Old English 'bæc' and 'up' from Old English 'up'; the phrasal verb 'back up' existed in earlier English and the single-word noun 'backup' developed later (20th century) as a compound used for 'reserve' or 'copy'.

Initially it was associated with the idea of moving or supporting from the rear; over time it developed the specialized senses of 'a reserve/substitute' and, with computing, 'a copy of data for recovery'.