'petal-less' originates from the English combination of the noun 'petal' (from Greek 'petalon' via Latin/French) and the English suffix '-less' (from Old English 'lēas'), where 'petal' meant 'leaf or leaf-like part (of a flower)' and '-less' meant 'without/free from'.

The element 'petal' entered English from French 'pétale', ultimately from Greek 'petalon' meaning 'leaf, petal'. The suffix '-less' comes from Old English 'lēas' and has been used productively in Middle and Modern English to form adjectives meaning 'without X', producing compounds such as 'petal-less' in Modern English.

Initially, the components denoted 'petal' (a leaf-like floral part) and '-less' ('without'); together they have retained the straightforward modern meaning 'without petals'.