coup de grâce vs deathblow

coup de grâce

noun
  • A final blow or shot given to kill a wounded person or animal. 

  • A remarkable finishing action. 

deathblow

noun
  • A strike or blow that leads to death, especially a coup de grace. 

  • Something that prevents the completion, or ends the existence, of a project etc.; a fatal setback. 

How often have the words coup de grâce and deathblow occurred in a corpus of books? (source: Google Ngram Viewer )