'polymorphous-leaved' originates from Modern English, formed by combining the Greek-derived element 'polymorphous' (ultimately from Greek 'polymorphos') and the Old English word 'lēaf' ('leaf'), where 'poly-' meant 'many' and 'morphē' meant 'form'.

'polymorphous' changed from Greek 'polymorphos' into Late Latin/Medieval forms and then into Middle/Modern English as 'polymorphous'; the adjective was later combined with the Old English-derived adjective-forming 'leaved' to produce the compound 'polymorphous-leaved'.

Initially the Greek element meant 'many-formed' in a general sense; over time in botanical English it evolved to describe plants that have leaves of different shapes, i.e., 'having many-shaped leaves'.