'incongruity' originates from Late Latin, specifically the word 'incongruitas', where 'in-' meant 'not' and 'congruit-' (from 'congruere') meant 'to come together' or 'agree'.

'incongruitas' passed into Old French as 'incongruité' and then into Middle English as 'incongruity', eventually yielding the modern English noun 'incongruity' (and its plural 'incongruities').

Initially, it meant 'lack of agreement or coming together' (a state of not fitting together), and over time it has come to mean more generally 'a lack of harmony, appropriateness, or consistency' in modern usage.