sheepdog vs warden

sheepdog

noun
  • A police officer. 

  • A breed of dog, used for herding sheep. 

  • A breed of dog used for guarding sheep. 

verb
  • To chaperon or shepherd. 

warden

noun
  • A chief administrative officer of a prison. 

  • An official charged with supervisory duties or with the enforcement of specific laws or regulations; such as a game warden or air-raid warden 

  • A variety of pear. 

  • A governing official in various institutions 

verb
  • To carry out the duties of a warden. 

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