bagpipes vs shawm

bagpipes

noun
  • A musical wind instrument of Celtic origin, possessing a flexible bag inflated by bellows, a double-reed melody pipe and up to four drone pipes; any aerophone that produces sound using air from a reservoir to vibrate enclosed reeds. 

shawm

noun
  • A mediaeval double-reed wind instrument with a conical wooden body. 

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