filicide vs first-degree murder

filicide

noun
  • The killing of one's own child. 

  • A person who kills their own child. 

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. 

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