'dual-role' is a compound formed in modern English from 'dual' + 'role'. 'dual' originates from Latin 'dualis', from 'duo' meaning 'two'; 'role' originates from French 'rôle', from Medieval Latin 'rotulus' meaning 'roll' (a list or register).

'dual' came into English via Latin 'dualis' (from 'duo' meaning 'two'), while 'role' entered from French 'rôle' (from Medieval Latin 'rotulus'). The compound 'dual role' (often hyphenated as 'dual-role') developed in 20th-century English to describe combined functions.

Initially the parts meant 'two' (dual) and 'roll/part in a play or function' (role); over time they combined to refer specifically to a single person or thing performing two functions, which is the current meaning.