Rocky Mountain canary vs jenny

Rocky Mountain canary

noun
  • A burro. 

jenny

noun
  • A device for spinning thread from fiber onto multiple spindles (also called spinning jenny). 

  • A catmill. 

  • In billiards and similar games, a powerful follow shot with plenty of topspin. 

  • A female creature of certain kinds, such as wren and donkey. 

verb
  • To wind finished lace onto cards ready for sale. 

How often have the words Rocky Mountain canary and jenny occurred in a corpus of books? (source: Google Ngram Viewer )