'non-petalous' originates from Modern English, formed by the prefix 'non-' (from Latin 'non' meaning 'not') combined with 'petalous' (from Greek 'petalon' meaning 'leaf' or 'petal').

'petal' comes from Greek 'petalon', passed into Neo-Latin as 'petalum' and French 'pétale', then entered English as 'petal'; the adjective 'petalous' was formed from that root, and 'non-' was prefixed in Modern English to create 'non-petalous'.

Initially it literally combined 'not' + 'having petals' and its meaning—'not having petals'—has remained consistent in botanical use.