embolism vs embolus

embolism

noun
  • An obstruction or occlusion of an artery by an embolus, that is by a blood clot, air bubble or other matter that has been transported by the blood stream. 

  • An intercalated prayer for deliverance from evil coming after the Lord's Prayer. 

  • The insertion or intercalation of days into the calendar in order to correct the error arising from the difference between the civil year and the solar year. 

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 embolism and embolus occurred in a corpus of books? (source: Google Ngram Viewer )