musical glasses vs verrillon

musical glasses

noun
  • The glass harp (musical instrument made up of a series of glasses) or similar earlier instrument. 

verrillon

noun
  • The glass harp: a musical instrument consisting of an array of glasses filled with varying amounts of water, played by rubbing one's fingers around the rims of the glasses. 

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