'unlock' originates from Old English, specifically the word 'unlocian,' where 'un-' meant 'not' and 'locian' meant 'to fasten or close.'

'unlocian' transformed into the Middle English word 'unlocken,' and eventually became the modern English word 'unlock.'

Initially, it meant 'to open or unfasten something,' and this meaning has largely remained the same in modern usage.