coalescence vs embolus

coalescence

noun
  • The merging of two segments into one. 

  • The act of coalescing. 

embolus

noun
  • An obstruction causing an embolism: a blood clot, air bubble or other matter carried by the bloodstream and causing a blockage or occlusion of a blood vessel. 

  • The structure on the end of the palp of male arachnids which contains the opening to the ejaculatory duct. 

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