'dual-purpose' originates from combining two English elements: 'dual' (from Latin, specifically the word 'dualis', ultimately from 'duo'), where 'duo' meant 'two'; and 'purpose' (from Old French, specifically the word 'porpos' or 'pourpos', ultimately from Latin 'propositum'), where 'pro-' meant 'forth' and 'positum/ponere' related to 'to place/put'.

'dual-purpose' developed as a compound in modern English by joining the adjective 'dual' (from Latin 'dualis' via Middle English) with the noun 'purpose' (from Old French 'porpos' < Latin 'propositum'), producing the compound meaning seen in contemporary English.

Initially it literally denoted 'having two purposes'; over time the meaning has remained largely stable and continues to mean 'serving two functions or uses'.