hammered dulcimer vs santoor

hammered dulcimer

noun
  • A type of dulcimer whose metal strings are stretched over a trapezoidal sounding board that has two bridges, one bass and one treble, set on a stand and played with small mallet-like hammers. 

santoor

noun
  • An Indian string instrument, a trapezoidal hammered dulcimer with seventy strings, believed to be derived from the Persian santur. 

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