desultory vs erratic

desultory

adj
  • Jumping, or passing, from one thing or subject to another, without order, planning, or rational connection; lacking logical sequence. 

  • Disappointing in performance or progress. 

  • Out of course; by the way; not connected with the subject. 

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. 

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