'noncontagious' originates from the prefix 'non-' meaning 'not' and the word 'contagious', which comes from Latin 'contagiosus', meaning 'communicable by contact'.

'contagiosus' transformed into the Old French word 'contagieux', and eventually became the modern English word 'contagious'. The prefix 'non-' was added to form 'noncontagious'.

Initially, 'contagious' meant 'communicable by contact', and 'noncontagious' has consistently meant 'not communicable by contact'.