'patch-up' is formed in English from the noun/verb 'patch' and the particle 'up'. 'patch' originates from Middle English 'pach(e)' (from Old French 'pache'), meaning 'a piece used to mend', and 'up' originates from Old English 'upp', meaning 'up' or indicating completion.

'patch' entered English as Middle English 'pach(e)' from Old French 'pache'; 'up' comes from Old English 'upp'. The compound phrasal verb 'patch up' arose in Modern English to mean 'to mend', and the hyphenated noun 'patch-up' developed to denote the result or a temporary reconciliation.

Originally 'patch' referred specifically to a piece of material used for mending; 'patch up' first meant to physically mend or fasten something. Over time the phrase broadened metaphorically to include repairing relationships or making temporary fixes, yielding the noun sense 'patch-up' for a makeshift repair or truce.