brittleness vs inefficacy

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. 

inefficacy

noun
  • The condition of being ineffective 

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