hebetude vs idleness

hebetude

noun
  • Mental lethargy or dullness. 

idleness

noun
  • The state of being idle; inactivity. 

  • Groundlessness; worthlessness; triviality; vanity; frivolity. 

  • The state of being indolent; indolence. 

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