'nonexpansionist' originates from Modern English, specifically formed from the prefix 'non-' (from Latin the word 'non' meaning 'not') and the word 'expansionist' (from 'expansion', ultimately from Latin 'expansio').

'nonexpansionist' developed by combining the negative prefix 'non-' with 'expansionist'; 'expansionist' comes from the noun 'expansion' (Old French 'expansion', from Latin 'expansio' from 'expandere' meaning 'to spread out'), and the adjective/noun form 'expansionist' arose in modern English before 'nonexpansionist' was formed.

Initially it simply meant 'not expansionist' (a literal negation), but over time it has been used specifically in political and diplomatic contexts to mean 'opposed to territorial or political expansion'.