folly vs insanity

folly

noun
  • Foolishness that results from a lack of foresight or lack of practicality. 

  • a pinkish-red color 

  • A fanciful building built for purely ornamental reasons. 

  • Thoughtless action resulting in tragic consequence. 

insanity

noun
  • The state of being insane; madness. 

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