coup de grâce vs lethal

coup de grâce

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

  • A remarkable finishing action. 

lethal

noun
  • Any weapon that causes death. 

  • One of the higher alcohols of the paraffine series obtained from spermaceti as a white crystalline solid. 

  • An allele that causes the death of the organism that carries it. 

adj
  • Of, pertaining to, or causing death; deadly; mortal; fatal. 

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