Berserkers (or berserks) were champion Norse warriors who are primarily reported in Icelandic literature to have fought in a trance-like fury, a characteristic which later gave rise to the English word berserk.
These champions would often go into battle without mail-coats. Berserkers are attested to in numerous Old Norse sources, as were the Ulfhednar (wolf-coats).
The English word berserker is derived from the Old Norse words ber-serkr (plural ber-serkir) meaning a "bear-shirt" i.e. a wild warrior or champion of the heathen age, however its interpretation remains controversial. The element ber- was interpreted by the historian Snorri Sturluson as "bare", which he understood to mean that the warriors went into battle bare-chested, or without armor. This word is also used in ber-skjaldaðr that means "bare of shield", or without a shield. Others derive it from the preferred berr (Germ, bär = ursus, the bear), and Snorri's view has been largely abandoned.
It is proposed by some authors that the northern warrior tradition originated in hunting magic, and by the time of the Germanic Heroic Age it had developed into a physical and spiritual form of martial arts comparable to the Japanese Samurai code of Bushido. Its values included self-reliance, self-control, strict training, able to perform feats with weapons, and to be willing to die selflessly defending family and companions. It was a religious code. Later, the coming of Christianity would transform the religious element into the chivalrous knight and the animal totems into heraldic devices. Three main animal cults appeared in the northern martial arts: the bear, the wolf, and the wild boar.
The bas relief carvings on Trajan's column in Rome depict scenes of Trajan's conquest of Dacia in 101-106 AD. The scenes show his Roman soldiers plus auxiliaries and allies from Rome's border regions, including tribal warriors from both sides of the Rhine. There are warriors depicted as bare-foot, bare-chested, bearing weapons and helmets that are associated with the Germani. Scene 36 on the column shows some of these warriors standing together, with some wearing bearhoods and some wearing wolfhoods. Nowhere else in history are Germanic bear-warriors and wolf-warriors fighting together recorded until 872 AD, with Thórbiörn Hornklofi's description of the battle of Hafrsfjord when they fight together for King Harald Fairhair of Norway.