demurral vs protestation

demurral

noun
  • A formal objection. 

  • The act of demurring. 

protestation

noun
  • a formal solemn objection or other declaration 

  • A declaration in common-law pleading, by which the party interposes an oblique allegation or denial of some fact, protesting that it does or does not exist, and at the same time avoiding a direct affirmation or denial. 

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