cockroach vs insect

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. 

insect

noun
  • A contemptible or powerless person. 

  • An arthropod (in the Insecta class) characterized by six legs, up to four wings, and a chitinous exoskeleton. 

  • Any small arthropod similar to an insect, including spiders, centipedes, millipedes, etc. 

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