'antioptimism' originates from modern English, specifically the combination of the prefix 'anti-' and the noun 'optimism', where 'anti-' meant 'against' (from Greek) and 'optimism' referred to 'a tendency to expect the best' (from Latin/French via 'optimum').

'anti-' comes from Greek 'anti-' meaning 'against', while 'optimism' developed from French and Latin (Latin 'optimum' meaning 'best') into English 'optimism' in the 18th century; the compound 'antioptimism' is a more recent coinage using the productive English prefixing pattern and so formed in modern English usage.

Initially the elements meant 'against' + 'best/hopefulness', and over time the compound has come to denote either a formal opposition to the doctrine of optimism or a more general pessimistic tendency; the basic sense 'against optimism' has remained central.