spiracle vs ventilation

spiracle

noun
  • Any small aperture or vent for air or other fluid. 

  • A pore or opening used (especially by arthropods and some fish) for respiration. 

  • The blowhole of a whale, dolphin or other similar species. 

ventilation

noun
  • The replacement of stale or noxious air with fresh. 

  • The bodily process of breathing; the inhalation of air to provide oxygen, and the exhalation of spent air to remove carbon dioxide. 

  • An exchange of views during a discussion. 

  • The mechanical system used to assist breathing. 

  • The public exposure of an issue or topic. 

  • The mechanical system used to circulate and replace air. 

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