shrill vs snorkel

shrill

verb
  • To make a shrill noise. 

noun
  • A shrill sound. 

adj
  • Sharp or keen to the senses. 

  • Having a shrill voice. 

  • Fierce, loud, strident. 

  • High-pitched and piercing. 

snorkel

verb
  • To use a snorkel. 

noun
  • A snorkel parka. 

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

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

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