'noncontagiousness' originates from English, formed by the negative prefix 'non-' (from Latin 'non', meaning 'not'), the adjective 'contagious' (from Latin 'contagiosus' via Old French), and the noun-forming suffix '-ness' (from Old English '-nessa', indicating a state or quality).

'contagious' developed from Latin 'contagiosus' (related to 'contagionem'/'contagion') into Old French and then Middle English as 'contagious'; the productive English prefix 'non-' was added to create 'noncontagious', and the abstract noun-forming suffix '-ness' produced 'noncontagiousness'.

Initially the components meant 'not' + 'spreading by contact' + 'state/quality'; over time this composition came to be used in English to denote specifically 'the state of not being contagious', a meaning that has remained stable in modern usage.