expostulate vs falsetto

expostulate

verb
  • To protest or remonstrate; to reason earnestly with a person on some impropriety of conduct. 

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 expostulate and falsetto occurred in a corpus of books? (source: Google Ngram Viewer )