cockroach vs ratfink

cockroach

noun
  • A person or a member of a group of people regarded as undesirable and rapidly procreating. 

  • A Tutsi. 

  • A person from New South Wales. 

  • A black or brown straight-winged insect of the order Blattodea. 

ratfink

noun
  • A dislikable or contemptible person. 

  • An informer or spy; a traitor. 

verb
  • To inform on; to betray. 

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