'backdown' originates from English, formed by combining the verb 'back' and the adverb 'down'; 'back' ultimately comes from Old English 'bæc' meaning 'back, rear' and 'down' comes from Old English 'dūn' (and related Old Norse forms) meaning 'down' or 'lower'.

'back down' developed in Middle English as a literal phrase meaning to move backward or downwards; by later English it had become a phrasal verb with figurative senses ('withdraw, yield'), and the noun form 'backdown' was later coined from that verb phrase.

Initially it referred to literal backward or downward movement, but over time it evolved into the figurative sense 'to withdraw a claim or position' and the noun for that act.