folly vs rationale

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. 

rationale

noun
  • An explanation of the basis or fundamental reasons for something. 

  • A liturgical vestment worn by some Christian bishops of various denominations. 

  • A justification or rationalization for something. 

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