fratricide vs massacre

fratricide

noun
  • The intentional or unintentional killing of a comrade in arms. 

  • A person who commits fratricide. 

  • The killing of one's brother (or sister). 

  • The undesirable situation where the separate missiles from a MIRV interfere with each other as they explode. 

massacre

noun
  • The killing of a considerable number (usually limited to people) where little or no resistance can be made, with indiscriminate violence, without necessity, and contrary to civilized norms. 

  • St. Bartholomew's Day Massacre 

  • Any overwhelming defeat, as in a game or sport. 

verb
  • To win against (an opponent) very decisively. 

  • To perform (a work, such as a musical piece or a play) very poorly. 

  • To kill with great force or brutality. 

  • To kill in considerable numbers where little or no resistance can be made, with indiscriminate violence, without necessity, and contrary to civilized norms. (Often limited to the killing of human beings.) 

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