berserk

Etymology

From berserker, a Norse warrior, a word introduced (as berserkar) by Sir Walter Scott in The Pirate (1822).^[1] It is borrowed from Old Norse berserkr (“raging warrior of superhuman strength”),^[1][2] probably from ber- “bear” + serkr “shirt”, i.e. “bear-coat”.^[2][3] Scott evidently took it instead from berr “bare”, as a warrior who fought without armour.^[1]

The adjective, as in go berserk, is recorded from 1844.^[1] Compare bear and sark.^[1]

References

1. [1] [2] [3] [4] [5] Harper, Douglas, Online Etymology Dictionary, https://www.etymonline.com
2. [1] [2] Merriam-Webster's Collegiate Dictionary, Springfield, Mass.: Merriam-Webster
3. [1] Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press