flexibility vs mobility

flexibility

noun
  • The quality of being flexible; suppleness; pliability. 

  • The quality of having options. 

mobility

noun
  • The ability to move; capacity for movement. 

  • 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. 

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