'posteriority' originates from Latin, specifically from 'posterior' (from 'posterus'), where 'posterus' meant 'coming after'.

'posteriority' developed by attaching the Latin-derived suffix '-ity' to 'posterior' (from Late Latin/post-classical Latin forms such as 'posterioritas'/'posterioritas'), entering Middle and Early Modern English in forms meaning the state of being posterior and becoming the modern English noun 'posteriority'.

Initially it meant 'the state of coming after' in a temporal or positional sense; over time the core meaning has remained largely the same, though occasional rare uses extended it to imply secondary or inferior status.