'berserk' originates from Old Norse, specifically the word 'berserkr', where 'ber-' meant 'bear' and 'serkr' meant 'shirt'.

'berserkr' transformed into the Old English word 'berserker', and eventually became the modern English word 'berserk'.

Initially, it referred to Norse warriors who fought with a wild, uncontrolled fury, but over time it evolved into its current meaning of 'in a state of violent or destructive rage'.