FED vs eidolon

FED

noun

  • Field emission display. 

name

  • Federal Reserve System. Alternative spelling of Fed 

eidolon

noun

  • A phantom, a ghost or elusive entity. 

  • An image or representation of an idea; a representation of an ideal form; an apparition of some actual or imaginary entity, or of some aspect of reality. 

  • An unsubstantial image, spectre, phantom. 

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