'asininity' originates from Latin, specifically the word 'asinus', where 'asinus' meant 'ass' (donkey).

'asininity' developed from the adjective 'asinine' (from Latin 'asininus', 'of or pertaining to an ass') with the addition of the suffix '-ity' in English to form the noun meaning 'the quality of being asinine'.

Initially it referred literally to characteristics 'of or like an ass'; over time it became figurative for 'stupid or foolish', and now 'asininity' means 'foolishness' or 'stupid behavior'.