bedbug vs earthworm

bedbug

noun
  • A small nocturnal insect (Cimex lectularius), of the family Cimicidae, that feeds on the blood of humans and other warm-blooded hosts. 

earthworm

noun
  • A worm of the family Lumbricidae, or, more generally, of the suborder Lumbricina. 

  • A worm that lives in the ground. 

  • A contemptible person; a groveller. 

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