idleness vs inactivity

idleness

noun
  • The state of being idle; inactivity. 

  • Groundlessness; worthlessness; triviality; vanity; frivolity. 

  • The state of being indolent; indolence. 

inactivity

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

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