clef vs cliff

clef

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

cliff

noun
  • A vertical (or nearly vertical) rock face. 

  • A point where something abruptly fails or decreases in value etc. 

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