headsman vs slaughterman

headsman

noun
  • One in command of a whaling vessel. 

  • 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. 

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

slaughterman

noun
  • A man employed to slaughter animals in a slaughterhouse. 

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