'nonreligiousness' originates from Modern English, formed by the prefix 'non-' + the adjective 'religious' + the nominalizing suffix '-ness', where 'non-' meant 'not', 'religious' derived from Latin via Old French, and '-ness' forms nouns indicating a state or quality.

'religious' comes from Latin 'religiosus' (from 'religio'), passed into Old French as 'religieux/religieus' and into Middle English as 'religious'; the negative prefix 'non-' is a productive Modern English prefix added to form 'nonreligious', and adding '-ness' produced the noun 'nonreligiousness'.

Initially, Latin 'religio' referred to 'care, scruple, reverence', and 'religious' signified being connected with religion; over time the compound 'nonreligiousness' has come to mean simply the absence of that religious connection or belief.