culpable homicide vs fratricide

culpable homicide

noun
  • Used other than figuratively or idiomatically: see culpable, homicide. 

  • Homicide which is culpable but does not rise to the level of murder; unlawful killing of a human being which does not constitute murder. 

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. 

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