koto vs qin

koto

noun
  • A Japanese stringed instrument having numerous strings, usually seven or thirteen, that are stretched over a convex wooden sounding board and are plucked with three plectra, worn on the thumb, index finger, and middle finger of one hand. 

qin

noun
  • Any of several traditional Chinese musical instruments, most commonly the seven-stringed instrument more specifically called the guqin. 

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