embolus vs thrombosis

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. 

thrombosis

noun
  • The formation of thrombi in the blood vessels of a living organism, causing obstruction of the circulation. 

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