estray vs wild 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. 

wild cat

noun
  • An undomesticated felid, as tigers or lions. 

  • A feral cat. 

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