caitiff vs viperish

caitiff

adj

  • Especially despicable; cowardly 

noun

  • A base or despicable person; a wretch 

viperish

adj

  • spiteful; treacherous 

  • In the manner of a viper. 

How often have the words caitiff and viperish occurred in a corpus of books? (source: Google Ngram Viewer )