erratic vs undisturbed

erratic

adj
  • Deviating from normal opinions or actions; eccentric; odd. 

  • Unsteady, random; prone to unexpected changes; not consistent. 

noun
  • A rock moved from one location to another, usually by a glacier. 

  • Anything that has erratic characteristics. 

undisturbed

adj
  • not disturbed or agitated 

  • calm 

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