'pistillate-only' is a Modern English compound formed from 'pistillate' (from 'pistil') + 'only'. 'Pistillate' ultimately derives from Latin 'pistillum' ('pestle'), via New Latin/modern botanical usage 'pistil' meaning the female organ of a flower; 'only' comes from Old English 'ānlic/ān' meaning 'one' or 'single'.

'pistillate' developed in botanical English from 'pistil' (Late 17th–19th century botanical term) meaning the female organ, itself from Latin 'pistillum' 'pestle'. The compound 'pistillate-only' is a modern descriptive formation (20th century onward) combining that adjective with 'only' to emphasize exclusivity.

Originally 'pistillum' referred to a 'pestle'; over time the related word 'pistil' came to mean the female part of a flower, and 'pistillate' came to mean 'having pistils'. 'Pistillate-only' narrows this to mean 'having pistils exclusively (no stamens)'.