eon vs the past

eon

noun
  • A long period of time. 

  • A period of 1,000,000,000 years. 

  • The longest geochronologic unit, being a period of hundreds of millions of years; subdivided into eras. 

  • Eternity. 

  • A spirit being emanating from the Godhead. 

the past

noun
  • the period of time that has already happened 

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