aeon vs era

aeon

noun
  • Each universe in a series of universes, according to conformal cyclic cosmology. 

  • A spirit being emanating from the Godhead. 

era

noun
  • A geochronologic unit of tens to hundreds of millions of years; a subdivision of an eon, and subdivided into periods. 

  • A time period of indeterminate length, generally more than one year. 

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