churr vs pipe up

churr

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

noun
  • A low vocal sound made by some birds. 

pipe up

verb
  • To begin singing or playing musical notes on a pipe or similar wind instrument. 

  • To begin to blow more vigorously. 

  • To speak up, especially in a robust, assertive manner; to say something suddenly. 

  • To call, awaken, or summon, as with a musical instrument. 

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