1911 Encyclopædia Britannica/Berserker
BERSERKER (from the “sark” or shirt of the “bear,” or other animal-skins worn by them), in Scandinavian mythology, the name of the twelve sons of the hero Berserk, grandson of the eight-handed Starkadder and Alfhilde. Berserk was famed for the reckless fury with which he fought, always going into battle without armour. By the daughter of King Swafurlam, whom he had killed, he had the twelve sons who were his equals in bravery. In Old Norse the term berserker thus became synonymous with reckless courage, and was later applied to the bodyguards of several of the Scandinavian heroes.