Hang vs chirl

Hang

noun
  • A musical instrument invented and built by PANArt Hangbau AG, somewhat resembling a steelpan. 

chirl

noun
  • A kind of musical warble. 

verb
  • To emit a low sound; to warble. 

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