inactivity vs inertness

inactivity

noun
  • The quality of being inactive; idleness; passiveness. 

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 inactivity and inertness occurred in a corpus of books? (source: Google Ngram Viewer )