assassinate vs put to death

assassinate

verb
  • To murder someone, especially an important person, by a sudden or obscure attack, especially for ideological or political reasons. 

  • To harm, ruin, or defame severely or destroy by treachery, slander, libel, or obscure attack. 

put to death

verb
  • To kill as punishment for capital crimes; to execute. 

How often have the words assassinate and put to death occurred in a corpus of books? (source: Google Ngram Viewer )