cockroach vs flea

cockroach

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

  • A Tutsi. 

  • A person from New South Wales. 

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

flea

noun
  • A small, wingless, parasitic insect of the order Siphonaptera, renowned for its bloodsucking habits and jumping abilities. 

  • A thing of no significance. 

verb
  • To remove fleas from (an animal). 

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