churr vs keening

churr

noun
  • A low vocal sound made by some birds. 

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

keening

noun
  • An unpleasant wailing sound. 

  • Intense mournful wailing after a death, often at a funeral or wake 

adj
  • Sharp, shrill, especially of a sound. 

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