mass killing vs witch-hunt

mass killing

witch-hunt

verb
  • To perform a witch-hunt. 

noun
  • A public or political campaign or investigation which smears a person or group. 

  • An attempt to find and punish or harass a group of people perceived as a threat, usually on ideological or political grounds. 

  • A search for people believed to be using sorcery or harmful magic, typically in order to persecute or punish them. 

How often have the words mass killing and witch-hunt occurred in a corpus of books? (source: Google Ngram Viewer )