mistake vs unmasking

mistake

noun
  • An error; a blunder. 

  • A pitch which was intended to be pitched in a hard-to-hit location, but instead ends up in an easy-to-hit place. 

verb
  • To understand wrongly, taking one thing or person for another. 

unmasking

noun
  • The act by which somebody or something is unmasked. 

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