caitiff vs poltroon

caitiff

noun
  • A base or despicable person; a wretch 

adj
  • Especially despicable; cowardly 

poltroon

noun
  • An ignoble or total coward; a dastard; a mean-spirited wretch. 

adj
  • Cowardly. 

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