'unheated' originates from the prefix 'un-' meaning 'not' and the word 'heated' from Old English 'hǣtan', meaning 'to make hot'.

'heated' changed from the Old English word 'hǣtan' and eventually became the modern English word 'heated'.

Initially, it meant 'to make hot', but over time it evolved into its current meaning of 'lacking heat' when combined with 'un-'.