'non-laxative' originates from Modern English, formed by the negative prefix 'non-' (meaning 'not') combined with 'laxative'.

'laxative' ultimately comes from Latin 'laxare' meaning 'to loosen', via Late Latin 'laxativus' and Old French/French forms (e.g. 'laxatif') into Middle/Modern English 'laxative'; 'non-' is a native English prefix used to negate adjectives and nouns, producing 'non-laxative' in Modern English.

Originally elements related to 'lax-' meant 'loose' or 'to loosen'; over time 'laxative' came to mean 'a substance that promotes bowel movements', and 'non-laxative' developed to mean 'not producing that effect'.