High Quality Content by WIKIPEDIA articles! Berserkers (or berserks) were Norse warriors who are reported in the Old Norse literature to have fought in a nearly uncontrollable, trance-like fury, a characteristic which later gave rise to the English word berserk. Berserkers are attested in numerous Old Norse sources. Most historians believe that berserkers worked themselves into a rage before battle, but some think that they might have consumed drugged foods.