berserk [E19th] A berserker was an ancient Norse warrior who fought with wild, uncontrolled ferocity—he went berserk. The name came from an old Scandinavian word, berserkr, which probably meant ‘bear coat’ or ‘bearskin’, a suitably rugged garment for a terrifyingly unhinged Viking. An alternative possibility is that the first element is the equivalent of ‘bare’, referring to fighting without armour. The phrase to go berserk is first recorded in 1896.