'inessentiality' originates from English, specifically from the adjective 'inessential' + the noun-forming suffix '-ity', where the prefix 'in-' meant 'not' and 'essential' traces to Latin 'essentialis' (from 'essentia') meaning 'essence'.

'inessential' developed from the combination of the negative prefix 'in-' and 'essential' (from Medieval Latin 'essentialis' and Latin 'essentia' from 'esse' meaning 'to be'); adding the suffix '-ity' (from Latin '-itas') formed the noun 'inessentiality' in modern English.

Initially it referred to 'not of the essence' (i.e., 'not essential'); over time it has come to be used more generally for the 'lack of necessity or importance' in contemporary usage.