'dual-functionality' is a compound of 'dual' and 'functionality'. 'dual' originates from Latin, specifically the word 'dualis' (related to 'duo'), where 'duo' meant 'two'. 'functionality' originates from Latin via French and English: 'function' comes from Latin 'functio', where 'fungi' meant 'to perform', and the suffix '-ality' derives from Latin '-alitas'/'-itas' indicating 'state or quality'.

'dual' entered English from Latin (via Old French in some cases) as 'dualis' → Old French/Medieval Latin forms → Middle English 'dual'. 'function' passed into English from Latin 'functio' through Old French 'fonction', and the noun 'functionality' is a later Modern English formation built from 'function' + the abstract noun-forming suffix '-ality'.

Initially, 'dual' meant simply 'two' and 'functionality' referred to 'the state or quality of functioning'; over time, combined as 'dual-functionality' it came to mean 'the quality of having two functions or serving two purposes'.