'double-deal' originates from an English compound of 'double' + 'deal'. 'Double' comes to English via Old French and Middle English from Latin roots meaning 'twofold', and 'deal' comes from Old English 'dǣlan' meaning 'to divide, distribute' and later sense 'to handle' or 'to transact'.

'double' entered Middle English from Old French (e.g. 'double') ultimately from Latin 'duplex' (twofold). 'Deal' evolved from Old English 'dǣlan' to Middle English 'delen'/'delen' and came to include senses of 'to distribute' and 'to transact'; the compound 'double-deal' (and the related form 'double-dealing') arose in post-medieval English to describe dealing in a two-faced or duplicitous way.

Originally the elements meant 'twofold' and 'to deal/transact'; combined, the sense developed into 'to deal in two ways' and then into the modern sense of 'act deceitfully toward two sides' (i.e., duplicitous behavior).