buoyancy vs heaviness

buoyancy

noun
  • Resilience or cheerfulness. 

  • The ability of an object to stay afloat in a fluid. 

  • The upward force on a body immersed or partly immersed in a fluid. 

heaviness

noun
  • The state of being heavy; weight, weightiness, force of impact or gravity. 

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