churr vs let out

churr

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

noun
  • A low vocal sound made by some birds. 

let out

verb
  • Of sound, to emit. 

  • Of a school: to finish for the day or term, allowing the pupils to go home. 

  • To disclose. 

  • To rent out. 

  • To allow to operate at higher speed by adjusting controls. 

  • To release. 

  • To enlarge by adjusting one or more seams. 

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