'unequal-sepaled' originates as an English compound of two elements: 'unequal' (ultimately from Latin 'inaequalis', where 'in-' meant 'not' and 'aequalis' meant 'equal') and 'sepal' (from New Latin 'sepalum', a 19th-century botanical coinage derived from Greek 'skepē' meaning 'covering').

'unequal' passed into English via Old French and Middle English from Latin 'inaequalis'; 'sepal' was coined in botanical New Latin ('sepalum') in the 1800s and later combined with adjectives in English to form descriptive compounds such as 'unequal-sepaled'.

Initially the elements separately meant 'not equal' and 'a covering leaf'; combined in botanical usage they came to mean specifically 'having sepals of unequal size or shape'.