levity vs severity

levity

noun
  • A lighthearted or frivolous act. 

  • The state or quality of being light, buoyancy. 

  • Lightness of manner or speech, frivolity; lack of appropriate seriousness; inclination to make a joke of serious matters. 

severity

noun
  • The degree of something undesirable; badness or seriousness. 

  • The state of being severe. 

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