effusion vs overburden

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. 

overburden

noun
  • A sterile stratum that lies above the stratum being investigated 

  • The rock and subsoil that lies above a mineral deposit such as a coal seam. 

verb
  • To overload or overtax. 

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