manslaughter vs matricide

manslaughter

noun
  • The unlawful killing of a human, either in negligence or incidentally to the commission of some unlawful act, but without specific malice, or upon a sudden excitement of anger; considered less culpable than murder, but more culpable than justifiable homicide. 

matricide

noun
  • A person who kills his or her mother. 

  • The killing of one's mother. 

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