bowstring vs catgut

bowstring

noun
  • The string of an archer's bow. 

  • The string of an archer's bow, as used by the Turks for strangling offenders. 

verb
  • To strangle with a bowstring. 

catgut

noun
  • A cord of great toughness made from the intestines of animals, especially of sheep, used for strings of musical instruments, racquets, sutures etc. 

  • A sort of linen or canvas, with wide interstices. 

  • The material from which such cords are made. 

  • Tephrosia virginiana (goat's rue, devil's shoestring). 

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