'unlikely' originates from Old English, specifically the word 'unlicol', where 'un-' meant 'not' and 'licol' meant 'likely'.

'unlicol' transformed into the Middle English word 'unlikly', and eventually became the modern English word 'unlikely'.

Initially, it meant 'not having the appearance of truth', but over time it evolved into its current meaning of 'not likely to happen'.