Jack Ketch vs headsman

Jack Ketch

noun
  • the gallows 

  • death 

  • a public executioner 

  • the devil 

headsman

noun
  • 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. 

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

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