'double-dealing' originates from Modern English as a compound of 'double' and 'dealing'. 'Double' comes via Old French 'double' (from Latin 'duplex'/'duplus') meaning 'twofold', and 'deal' as a verb derives from Old English 'dǣlan' meaning 'to divide' (later taking senses of 'to transact' or 'to treat').

'double-dealing' developed from earlier uses of the adjective 'double' plus forms of the verb 'deal' (e.g., phrases like 'to double-deal' and the noun 'double-dealer'); by Early Modern English it was used to describe duplicitous conduct and eventually became the fixed compound 'double-dealing'.

Originally the elements simply meant 'twofold' ('double') and 'to transact' ('deal'), but together they evolved to denote duplicity; initially a literal sense of 'doing two deals' shifted to the figurative sense of acting in two-faced or deceitful ways, which is the modern meaning.