frivolity vs lightheartedness

frivolity

noun
  • frivolous act 

  • state of being frivolous 

lightheartedness

noun
  • An amusement or item of a pleasant but inconsequential nature. 

  • The state of being lighthearted, joyous, cheerful, without a care. 

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