immobility vs inertness

immobility

noun
  • The quality of not moving. 

  • The state or condition of being unable to change one's location, move or be moved. 

inertness

noun
  • Lack of activity or exertion; habitual indisposition to action or motion 

  • Absence of the power of self-motion; inertia. 

  • Quality of being unreactive with other chemical compounds or elements. 

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