clef vs discover

clef

noun
  • A symbol found on a musical staff that indicates the pitches represented by the lines and the spaces on the staff 

discover

verb
  • To find or learn something for the first time. 

  • To create by moving a piece out of another piece's line of attack. 

  • To question (a person) as part of discovery in a lawsuit. 

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