chirl vs convulse

chirl

verb
  • To emit a low sound; to warble. 

noun
  • A kind of musical warble. 

convulse

verb
  • To violently shake or agitate. 

  • To suffer violent involuntary contraction of the muscles, producing contortions of the body or limbs. 

  • To create great laughter. 

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