churr vs yip

churr

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

noun
  • A low vocal sound made by some birds. 

yip

verb
  • to bark with a sharp, high-pitched voice 

noun
  • a sharp, high-pitched bark 

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