'non-contagious' originates from the prefix 'non-' meaning 'not' and the word 'contagious' from Latin 'contagiosus', where 'contagion' meant 'contact, touch'.

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

Initially, 'contagious' meant 'capable of being transmitted by contact', and 'non-contagious' has consistently meant 'not capable of being transmitted by contact'.