parricide vs patricide

parricide

noun
  • The killing of a relative, especially a parent. 

  • Someone who kills a relative, especially a parent. 

  • The killing of a ruler, or other authority figure; treason. 

  • Someone who commits treason. 

patricide

noun
  • Murder of one's father. 

  • A murderer of his/her own father. 

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