'antioptimist' originates from Modern English, specifically the prefix 'anti-' (from Greek 'anti') meaning 'against' combined with 'optimist' (from French 'optimiste', ultimately from Latin 'optimus' meaning 'best').

'antioptimist' is a modern coinage formed by attaching the productive prefix 'anti-' to the noun 'optimist'; it is a direct formation (sometimes seen hyphenated as 'anti-optimist') rather than a word with a long historical lineage.

Initially it simply signified someone 'against optimism'; over time it has come to be used both as a neutral descriptor and as a mildly pejorative or humorous label for a persistently pessimistic person.