berserker (n.) Look up berserker at Dictionary.com
alternative form of berserk (q.v.), from Old Norse berserkr, accusative of berserk. This is the oldest form of the word in its revival in Modern English (1822), and perhaps Scott, who introduced it, mistook the -r for an agent-noun suffix. Further compicated because it has the form of the Old Norse plural, and English berserker sometimes is plural.