glass harp vs verrillon

glass harp

noun
  • A musical instrument consisting of glasses (typically wine glasses) tuned by putting different amounts of liquid into them. Sound is produced by rubbing one's fingers around the rims of the glasses, causing them to vibrate. 

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 glass harp and verrillon occurred in a corpus of books? (source: Google Ngram Viewer )