capper vs coup de grâce

capper

noun
  • A finale; something that is conclusively better, or "caps it all off". 

  • A person who caps i.e. is inclined to untruth, a fibber. 

  • A device or person that applies caps, as to bullets or bottles. 

  • A person who records a television broadcast to their computer. 

  • A person that makes or sells caps. 

coup de grâce

noun
  • A remarkable finishing action. 

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

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