Why is someone who is running wild said to be 'berserk?'

TabbyTom

A berserker was originally "a wild Norse warrior of great strength and ferocious courage, who fought on the battle-field with a frenzied fury known as the ‘berserker rage’" (Oxford English Dictionary). The etymology is uncertain. It probably refers to a "bear-sark" or bearskin garment that the warriors wore; but some people think it's "bare sark", meaning that they fought in a mere shirt with no outer armour. Sep 22 03, 9:03 AM

Hamlet.

Yes, in Norse mythology there was an actual warrior named Berserk. Berserk was invincible, and he chose to train his twelve sons to fight as ferociously as he did. Berserkers were commonly referred to as unbeatable and wildly unconventional foes. So they were described in Gods and Myths of Northern Europe: "...frantic as dogs or wolves; they bit their shields and were as strong as bears or boars, they slew men, but neither fire nor iron could hurt them." Sep 22 03, 9:16 AM