chirl vs quaver

chirl

noun
  • A kind of musical warble. 

verb
  • To emit a low sound; to warble. 

quaver

noun
  • A trembling of the voice, as in speaking or singing. 

  • A trembling shake. 

  • an eighth note, drawn as a crotchet (quarter note) with a tail. 

verb
  • To shake in a trembling manner. 

  • To use the voice in a trembling manner, as in speaking or singing. 

  • To utter quaveringly. 

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