'uneven-petaled' originates from Modern English, specifically the compound of 'uneven' and 'petaled', where 'uneven' meant 'not level or equal' and 'petaled' relates to 'petal' meaning 'a leaf-like segment of a flower'.

'uneven' developed from Old English elements: the prefix 'un-' (not) plus Old English 'efen' (even, level). 'Petal' derives from Greek 'petalon' (leaf), passed through Latin and French into Middle English as 'petal', and the past-participial/adjectival form 'petaled' was formed in Modern English to mean 'having petals'.

Initially the compound literally described petals that were not uniform; over time it has remained a literal descriptive term for flowers whose petals differ in size, shape, or arrangement.