She had had lots of power, in her own way, but she had no more motherly instinct than a berserk rhino.
- -- Gregory Maguire, Son of a Witch
In the explanation section of Word of the Day's entry for berserk, I enjoyed this etymology:
The English usage of berserk lies in an Old Norse story introduced by Sir Walter Scott in 1822. It is from the Old Norse word berserkr (n.) meaning a raging warrior of superhuman strength.
Linguistically, it probably from stems from ber- meaning bear and serkr meaning shirt, thus literally "a warrior clothed in bearskin."