first-degree murder vs patricide

first-degree murder

noun
  • An act that constitutes the crime of first-degree murder. 

  • The criminal offence of murder in a form considered by law to be the most serious; the precise distinction may vary by jurisdiction but typically involves premeditation, or the choice of victim or other circumstances being regarded as especially blameworthy. 

patricide

noun
  • Murder of one's father. 

  • A murderer of his/her own father. 

How often have the words first-degree murder and patricide occurred in a corpus of books? (source: Google Ngram Viewer )