assassin vs matricide

assassin

noun
  • Someone who intentionally kills a person, especially a professional who kills a public or political figure. 

  • Any ruthless killer. 

  • A member of the Nizari Ismaili Muslim community of the Alamut Period. 

verb
  • To assassinate. 

matricide

noun
  • A person who kills his or her mother. 

  • The killing of one's mother. 

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