'unobserved' originates from the prefix 'un-' meaning 'not' and the word 'observed' from Latin 'observare', where 'ob-' meant 'toward' and 'servare' meant 'to watch'.

'observare' transformed into the Old French word 'observer', and eventually became the modern English word 'observe', with 'un-' added to form 'unobserved'.

Initially, it meant 'not watched or noticed', and this meaning has largely remained the same in modern usage.