A warrior class, found among the Norse (or Vikings as they are commonly depicted). They fought on the battlefield with such fury that they needed no armour, and could bite through the iron of a shield and plunge through fire without pain. It was not uncommon for such a warrior to dress in the skins of a bear or to drink the blood of such a creature, in the hopes of gaining some of its strength. Hallucinogenic compounds were also taken to enahnce their rage. An extension from berserk, meaning to be of unsound mind, mad, insane, violently angry.

Likely derived from the words baresark (referring to the lack of armour) and bearsark (old Icelandic, literally "bear shirt").