'unwritten' originates from Old English, specifically the prefix 'un-' meaning 'not' and the word 'writen,' the past participle of 'writan,' meaning 'to write.'

'writen' transformed into the Middle English word 'writen,' and eventually became the modern English word 'written,' with 'un-' added to form 'unwritten.'

Initially, it meant 'not written down,' and this meaning has largely remained the same in modern usage.