'non-peaty' originates from the Latin prefix 'non' (meaning 'not') combined with English 'peaty', which is 'peat' plus the adjectival suffix '-y'.

'peat' comes from Old English 'pǣt' (Middle English 'pete'), which became modern English 'peat'; the adjective 'peaty' developed by adding '-y'; the prefix 'non-' (from Latin 'non') was later attached to form 'non-peaty' in modern English.

Initially it combined the negative prefix and the adjective to mean 'not peaty', and that basic negating meaning has remained stable into modern usage.