body louse vs crab louse

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. 

crab louse

noun
  • A parasitic insect, Pthirus pubis, that lives amongst the pubic hairs of humans and feeds on blood. 

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