'nightmare' originates from Middle English, specifically the word 'night' and 'mare', where 'mare' referred to a goblin that tormented people with frightening dreams.

'nightmare' changed from the Old English word 'mære' and eventually became the modern English word 'nightmare'.

Initially, it meant 'a goblin that tormented people with frightening dreams', but over time it evolved into its current meaning of 'a frightening or unpleasant dream'.