cavil vs falsetto

cavil

verb
  • To criticise for petty or frivolous reasons. 

noun
  • A petty or trivial objection or criticism. 

falsetto

verb
  • To sing or utter in falsetto. 

noun
  • A person who sings in falsetto. 

  • The "false" (singing) voice in any human, usually airy and lacking a purity of vowels; created by utilizing the next highest vocal folds above those used for speech and normal range singing. It is commonly confused with the head voice register. 

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