mustang vs yearling

mustang

noun
  • A small, hardy, naturalized (feral) horse of the North American west. 

  • A merchant marine who joined the U.S. Navy as a commissioned officer during the American Civil War. 

  • A commissioned officer who started military service as an enlisted person. 

verb
  • To hunt mustangs (wild horses), either for military use or for slaughter as pet food. 

yearling

noun
  • A racehorse that is considered to be one year old until a subsequent January 1st. 

  • A sophomore at West Point military academy. 

  • An animal that is between one and two years old; one that is in its second year (but not yet two full years old). 

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