idleness vs inertness

idleness

noun
  • The state of being idle; inactivity. 

  • Groundlessness; worthlessness; triviality; vanity; frivolity. 

  • The state of being indolent; indolence. 

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