at wits’ end vs berserk

at wits’ end

berserk

adj

  • Furiously, injuriously, or maniacally violent or out of control. 

  • Bizarre; weird. 

  • Wildly joyous; ecstatic. 

noun

  • Synonym of berserker (“a Norse warrior who fought in a frenzy”) 

How often have the words at wits’ end and berserk occurred in a corpus of books? (source: Google Ngram Viewer )