brittleness vs proneness

brittleness

noun
  • The state of being brittle; aptness to break; fragility. 

  • The property by virtue of which a material is fractured without appreciable deformation by the application of load. 

proneness

noun
  • The quality or state of being prone, or of bending downward. 

  • The state of lying with the face down. 

  • Inclination of mind, heart, or temper; propension; disposition. 

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