inflexibility vs steadfastness

inflexibility

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

steadfastness

noun
  • Loyalty in the face of trouble and difficulty. 

  • Steadfast resolution. 

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