Berserker Berserkers ( or berserks ) were Norse warrior s who are primarily 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 to 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 . The " Úlfhéðnar " ( singular Úlfheðinn ) , another term associated with berserkers , mentioned in the " Vatnsdœla saga " , " Haraldskvæði " and the " Völsunga saga " , were said to wear the pelt of a wolf when they entered battle . Úlfhéðnar are sometimes described as Odin ' s special warriors : " [ Odin ’ s ] men went without their mailcoats and were mad as hounds or wolves , bit their shields … they slew men , but neither fire nor iron had effect upon them . This is called ' going berserk . ' " In addition , the helm - plate press from Torslunda depicts ( below ) a scene of Odin with a berserker — " a wolf skinned warrior with the dancer in the bird - horned helm , which is generally interpreted as showing a scene indicative of a relationship between berserkgang … and the god Odin " — with a wolf pelt and a spear as distinguishing features . Etymology . The name " berserker " derives from the Old Norse " berserkr " ( plural " berserkir " ) . This expression most likely arose from their reputed habit of wearing a kind of shirt or coat ( " serkr " ) made from the pelt of a bear ( " ber - " ) during battle . The element " ber - " was sometimes interpreted as " berr - " , meaning " bare " , which Snorri understood to mean that the warriors went into battle bare - chested , or " without armor " as men of Odin . This view has since been largely abandoned . Terminology . To " go berserk " was to “ hamask ” which translates as “ change form , " in this case , a with the sense " enter a state of wild fury " and one who could transform as a berserker was typically thought of as “ hamrammr ” or “ shapestrong . ” For example , the band of men that go with Skallagrim in Egil ’ s Saga to see King Harald about his brother , Thorolf ’ s murder , they are described as , " all together there were twelve of them in the party , all the hardest of men , with a touch of the uncanny about a number of them … they [ were ] built and shaped more like trolls than human beings , " which is generally interpreted as this band of men being hamrammr . Attestations . Berserkers appear prominently in a multitude of other saga s and poems , many of which describe berserkers as ravenous men who loot , plunder , and kill indiscriminately . Later , by Christian interpreters , the berserk was even viewed as a " heathen devil . " The earliest surviving reference to the term " berserker " is in " Haraldskvæði " , a skaldic poem composed by Thórbiörn Hornklofi in the late 9th century in honour of King Harald Fairhair , as " ulfheðnar " ( " men clad in wolf skins " ) . This translation from the Haraldskvæði saga describes Harald ' s berserkers : The Icelandic historian and poet Snorri Sturluson ( 1179 – 1241 ) wrote the following description of berserkers in his " Ynglinga saga " : King Harald Fairhair ' s use of berserker " shock troops " broadened his sphere of influence . Other Scandinavian kings used berserkers as part of their army of hirdmen and sometimes ranked them as equivalent to a royal bodyguard . It may be that some of those warriors only adopted the organization or rituals of berserk männerbünde , or used the name as a deterrent or claim of their ferocity . Emphasis has been placed on the frenzied nature of the berserkers , hence the modern sense of the word ' berserk . ' However , the sources describe several other characteristics that have been ignored or neglected by modern commentators . Snorri ' s assertion that ' neither fire nor iron told upon them ' is reiterated time after time , and the sources frequently state that neither edged weapons nor fire affected the berserks , although they were not immune to clubs or other blunt instruments . For example : Similarly , Hrolf Kraki ' s champions refuse to retreat ' from fire or iron . ' Another frequent motif refers to berserkers blunting their enemy ' s blades with spells , or a glance from their evil eyes . This appears as early as Beowulf where it is a characteristic attributed to Grendel . Both the fire eating and the immunity to edged weapons are reminiscent of tricks popularly ascribed to Hindu fakir s . In 1015 , Jarl Eiríkr Hákonarson of Norway outlawed berserkers . Grágás , the medieval Icelandic law code , sentenced berserker warriors to outlawry . By the 12th century , organised berserker war - bands had disappeared . The Lewis Chessmen , found on the Isle of Lewis ( Outer Hebrides , Scotland ) but thought to be of Norse manufacture , include Berserkers depicted biting their shields . Theories . Scholar Hilda Ellis - Davidson draws a parallel between berserkers and the mention by the Byzantine emperor Constantine VII ( AD 905 – 959 ) in his book " De cerimoniis aulae byzantinae " ( " Book of Ceremonies of the Byzantine court " ) of a " Gothic Dance " performed by members of his Varangian Guard ( Norse warriors working in the service of the Byzantine Empire ) , who took part wearing animal skins and masks : she believes this may have been connected with berserker rites . The actual fit of madness the berserker experienced was referred to as " berserkergang " ( " going berserk " ) . This condition has been described as follows : Theories about what caused berserker behaviour include ingestion of materials with psychoactive properties , psychological processes , and medical condition s . Some scholars believe certain examples of berserker rage to have been induced voluntarily by the consumption of drugs such as the hallucinogenic mushroom " Amanita muscaria " . or massive amounts of alcohol . While such practices would fit in with ritual usages , other explanations for the berserker ' s madness have been put forward , including self - induced hysteria , epilepsy , mental illness or genetics . Jonathan Shay , MD , makes an explicit connection between the berserker rage of soldiers and the hyperarousal of post - traumatic stress disorder . In " Achilles in Vietnam " he writes : Modern context . The word " berserker " today applies to anyone who fights with reckless abandon and disregard to even his own life , a concept used during the Vietnam War and in Vietnam - inspired literature ( Michael Herr ' s " Dispatches " ) and film ( Oliver Stone ' s " Platoon " and Adrian Lyne ' s " Jacob ' s Ladder " ) . " Going berserk " in this context refers to an of adrenaline - induced opioid s ( or military - issued amphetamine for long missions ) in the human body and brain leading a soldier to fight with fearless rage and indifference , a state strikingly similar to that of the 9th century berserkers . " Going berserk " is also used colloquially to describe a person who is acting in a wild rage or in an uncontrolled and irrational manner . " Berserker " is also a well known character archetype and status in video games and other media .