executioner vs headsman

executioner

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

  • A hit man, especially being in some organization. 

headsman

noun
  • An executioner whose method of dispatching the condemned is decapitation. 

  • A labourer in a colliery who transports the coal from the workings to the horseway, and who is oftentimes assisted by a younger worker called a foal. 

  • One in command of a whaling vessel. 

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