estray vs farm cat

estray

noun
  • An animal that has escaped from its owner; a wandering animal whose owner is unknown. An animal cannot be an estray when on the range where it was raised, and permitted by its owner to run. A lost animal whose owner is known to the party at hand is not an estray. 

farm cat

noun
  • A domestic cat, usually of a mixed breed, that lives primarily outdoors, in a feral or semiferal condition on agricultural properties. 

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