gnat vs insect

gnat

noun
  • Any small insect of the order Diptera, specifically within the suborder Nematocera. 

  • An annoying person. 

insect

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

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

  • A contemptible or powerless person. 

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