'unequal-leaved' is a compound formed from 'unequal' + 'leaved'. 'Unequal' comes via Old French 'inegal' from Latin 'in-' (not) + 'aequalis' (equal). 'Leaved' is built from Old English 'leaf' + the adjectival suffix '-ed' indicating 'having leaves'.

'unequal' entered Middle English from Old French 'inegal' (from Latin 'inaequalis'), while 'leaf' derives from Old English 'lēaf'. The compound 'unequal-leaved' developed by combining the adjective 'unequal' with the adjective-forming 'leaved' to describe plants with unequal leaves.

Originally the elements meant 'not equal' and 'having leaves'; combined, they have retained the straightforward descriptive meaning 'having leaves that are not equal' and remain a specialized botanical descriptor.