definitive vs straight from horse’s mouth

definitive

noun
  • an ordinary postage stamp that is part of a series of all denominations or is reprinted as needed to meet demand 

  • a word, such as a definite article or demonstrative pronoun, that defines or limits something 

adj
  • conclusive or decisive 

  • general, not issued for commemorative purposes 

  • explicitly defined 

  • definite, authoritative and complete 

  • limiting; determining 

straight from horse’s mouth

How often have the words definitive and straight from horse’s mouth occurred in a corpus of books? (source: Google Ngram Viewer )