crab louse vs tabes dorsalis

crab louse

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

tabes dorsalis

noun
  • tabes of the back; a degeneration of the sensory neurons of the spinal cord carrying afferent information. 

  • neurosyphilis in the form of such degeneration. 

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