mobility vs stillness

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. 

stillness

noun
  • Habitual silence or quiet; taciturnity. 

  • The quality or state of being still. 

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