'non-expansionism' originates from English; it is formed by the prefix 'non-' meaning 'not', the noun 'expansion' (from Latin 'expansio'), and the suffix '-ism' denoting a doctrine or practice.

'expansion' comes from Latin 'expansio' (from 'expandere': ex- 'out' + pandere 'to spread'); this passed into Middle English via Old French as 'expansion'. The suffix '-ism' was added in modern English to form 'expansionism', and the prefix 'non-' was later attached to create 'non-expansionism' to denote the opposite doctrine.

Originally 'expansion' meant 'a spreading out' and 'expansionism' meant the policy or practice of expanding; over time the prefixed form 'non-expansionism' came to mean the deliberate policy of not expanding (i.e., opposition to expansionism).