churr vs growling

churr

noun
  • A low vocal sound made by some birds. 

verb
  • To make the low vocal sound of some birds. 

growling

noun
  • The technique of producing a low-pitched growling or rumbling sound on a wind instrument. 

  • A sustained instance of growls or guttural noises. 

adj
  • Producing a growl. 

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