bullwork vs thrall

bullwork

thrall

noun
  • The state of being under the control of another person. 

  • One who is enslaved or under mind control. 

  • A shelf; a stand for barrels, etc. 

verb
  • To make a thrall; enslave. 

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