'antisepalous' originates from Greek prefix 'anti-' (from Greek 'anti' meaning 'against, opposite') combined with the element 'sepalous' derived from Modern Latin 'sepalum' (from which English 'sepal' comes) and the adjectival suffix '-ous'.

'anti-' (Greek) + Modern Latin 'sepalum' gave English 'sepal' in the 19th century; from 'sepal' the adjective form 'sepalous' was formed, and 'antisepalous' developed by adding the prefix 'anti-' to mean 'against/without sepals'.

Initially formed simply by combining elements meaning 'against' + 'sepal', it came to be used specifically in botanical description to mean 'lacking sepals' or 'without sepals'.