'non-moralistic' originates from the prefix 'non-' (from Latin 'non' meaning 'not') combined with 'moralistic', which derives from 'moral' (from Latin 'moralis' meaning 'pertaining to manners or morals').

'moral' came into English via Latin 'moralis' and Old French 'moral'; from English 'moral' the adjective 'moralistic' was formed in Modern English, and the negating prefix 'non-' was later attached to form 'non-moralistic'.

Initially, elements like 'moral' meant 'pertaining to manners or morals'; over time 'moralistic' gained the sense of 'overly concerned with morals or inclined to moralize', and 'non-moralistic' now denotes the absence of that moralizing attitude.