fistula vs snorkel

fistula

noun
  • A tube, a pipe, or a hole. 

  • An abnormal connection or passageway between organs or vessels that normally do not connect. 

  • The tube through which the wine of the Eucharist was once sucked from the chalice in certain ceremonies (such as papal Masses). 

snorkel

noun
  • A retractable tube fitted in diesel-engine submarines to allow sufficient ventilation that the engines may be used at periscope depth. 

  • A snorkel parka. 

  • A hollow tube, held in the mouth, or mounted on and opening into a diving mask, used by swimmers for breathing underwater. 

verb
  • To use a snorkel. 

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