foal vs rocking horse

foal

noun
  • A young horse or other equine, especially just after birth or less than a year old. 

  • A young boy who assisted the headsman by pushing or pulling the tub. 

verb
  • To give birth to (a foal); to bear offspring. 

rocking horse

noun
  • a child’s toy consisting of a (usually wooden) horse mounted on a rocker or swing 

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