eyepiece vs peeper

eyepiece

noun
  • The lens (or combination of lenses) at the eye end of a microscope or telescope by which the image is viewed. 

peeper

noun
  • The eye. 

  • An animal, such as some frogs, having a shrill, high-pitched call. 

  • Someone who peeps; a spy. 

  • A chicken just breaking the shell; a young bird. 

  • A peeping tom. 

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