effusion vs spiracle

effusion

noun
  • The seeping of fluid into a body cavity; the fluid itself. 

  • Process of gases passing through a hole or holes considerably smaller than the mean free path of the gas molecules. 

  • An outpouring of speech or emotion. 

  • A liquid outpouring. 

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. 

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