FED vs penumbra

FED

noun
  • Field emission display. 

name
  • Federal Reserve System. Alternative spelling of Fed 

penumbra

noun
  • A partially shaded area around the edges of a shadow, especially an eclipse. 

  • An area of uncertainty or intermediacy between two mutually exclusive states or categories. 

  • A region around the edge of a sunspot, darker than the sun's surface but lighter than the middle of the sunspot. 

  • Something related to, connected to, and implied by, the existence of something else that is necessary for the second thing to be full and complete in its essential aspects. 

  • An area that lies on the edge of something; a fringe. 

  • A region of the brain that has lost only some of its blood supply, and retains structural integrity but has lost function. 

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