'non-nationalist' originates from Modern English, formed by the prefix 'non-' (from Latin 'non', meaning 'not') attached to 'nationalist' (from French 'nationaliste' / English 'nationalist').

'nationalist' developed from 'nation' (Latin 'natio', meaning 'birth, people') with the adjectival/agentive suffix (via French 'national' + '-iste' forming 'nationaliste') and entered English in the 19th century as 'nationalist'; the negating prefix 'non-' (used in English since Middle English, from Latin 'non') was later attached to create 'non-nationalist' in modern usage.

Originally, 'nationalist' meant 'one who advocates the interests or independence of a nation'; adding 'non-' produced a straightforward negation meaning 'not a nationalist' and the meaning has remained a direct negative of the base term.