Behave in a frenzied and violent manner.
This term has something in common with 'run amok'. The two phrases, as well as sounding rather similar, mean virtually the same thing. Their sources though could hardly be further apart. 'Run amok' derives from the Far East, whereas 'go berserk' is of Viking (Norse) origin. In that tradition a 'Berserker' was a warrior of great strength and courage, who fought with wild ferocity. The word is believed to be derived from 'bear sark', i.e. bear coat. That berserker fighting tradition, in which the warriors took on the spirit (or even in their belief, the shape) of bears whilst foaming at the mouth and gnawing the edges of their shields, is the source of the Vikings' fierce reputation. It dates back to the first millennium but had died out by the 1100s and thereafter the word berserker didn't feature widely in the English language until the 19th century. There is a rival, but less widely accepted, version of the derivation. In this the Vikings were supposed to show their bravery by going into battle with their sark jackets open, i.e. 'bare-sark'.
Who better to bring the word to our notice than that inveterate reviver of historical stories, Sir Walter Scott? In his 1822 book 'Pirate', he wrote:
"The berserkars were so called from fighting without armour."
It was quite some time before the word began to be used in the figurative sense, i.e. for it to be applied to people who 'went berserk' without an allusion to Viking warriors. Rudyard Kipling's book Diversity of Creatures, 1908 has:
"You went Berserk. I've read all about it in Hypatia ... you'll probably be liable to fits of it all your life."
The first reference I can find to the actual use of the term 'go berserk' is in the obscure US newspaper the La Crosse Tribune and Leader-Press, 1919:
"With hungry Russians crowding in from the east, a hungry Germany may shortly toss its new conventions after the old and go berserk in the teeth of the cannon."