'backdate' is formed in English from the word 'back' + the noun 'date' (the latter from Latin 'datum' via Old French 'date'), where 'back' originally meant 'the rear or earlier time' and 'date' referred to a specified day.

'date' entered English from Old French 'date', from Latin 'datum' ('given'); 'back' comes from Old English 'bæc'. The compound 'backdate' arose in modern English by combining these elements to mean assigning a previous date.

Originally a straightforward compound of 'back' + 'date', the term developed the specific sense of intentionally assigning an earlier date to a document or action.