laughter vs levity

laughter

noun
  • The sound of laughing, produced by air so expelled; any similar sound. 

  • A movement (usually involuntary) of the muscles of the laughing face, particularly of the lips, and of the whole body, with a peculiar expression of the eyes, indicating merriment, satisfaction or derision, and usually attended by a sonorous and interrupted expulsion of air from the lungs. 

levity

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

  • A lighthearted or frivolous act. 

  • The state or quality of being light, buoyancy. 

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