doggedness vs inflexibility

doggedness

noun
  • The state of being dogged; persistence; perseverance; tenacity; stubbornness. 

inflexibility

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

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