'pleonasm' originates from Greek, specifically the word 'πλεονασμός' (pleonasmós), where 'πλεόν' (pleón) meant 'more' or 'too much'.

'πλεονασμός' passed into Late Latin as 'pleonasmus' and into French as 'pléonasme'; English borrowed the word (as 'pleonasm') from these sources in the modern period.

Initially it referred broadly to 'excess' or 'overabundance'; over time it narrowed to mean excess in language—unnecessary words or redundancy in expression.