inflexibility vs mobility

inflexibility

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

mobility

noun
  • A tendency to sudden change; mutability, changeableness. 

  • The degree to which particles of a liquid or gas are in movement. 

  • People's ability to move between different social levels or professional occupations. 

  • The ability of a military unit to move or be transported to a new position. 

  • The ability to move; capacity for movement. 

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