'nonbeliever' originates from the prefix 'non-' meaning 'not' and the word 'believer', which comes from Old English 'belȳfan', meaning 'to believe'.

'belȳfan' transformed into the Middle English word 'bileven', and eventually became the modern English word 'believe'.

Initially, 'believe' meant 'to have faith or confidence in', and this meaning has largely remained the same in modern usage.