body louse vs underperson

body louse

noun
  • A parasitic insect, Pediculus humanus humanus (syn. Pediculus humanus corporis), that infests the body and clothes of humans and feeds on blood. 

underperson

noun
  • A member of a subhuman sentient species. 

  • A person of low status. 

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