executioner vs man-killer

executioner

noun
  • An official person who carries out the capital punishment of a criminal. 

  • A hit man, especially being in some organization. 

man-killer

noun
  • A murderer. 

  • An animal that kills humans. 

  • Someone who habitually seduces men. 

How often have the words executioner and man-killer occurred in a corpus of books? (source: Google Ngram Viewer )