inflexibility vs inflexibleness

inflexibility

noun
  • The quality or state of being inflexible, or not capable of being bent or changed; unyielding stiffness 

inflexibleness

noun
  • The quality or state of being inflexible 

  • Obstinacy of will or temper; firmness of purpose that will not yield to importunity or persuasion; unbending pertinacity. 

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