desultory vs halfhearted

desultory

adj
  • Disappointing in performance or progress. 

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

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

halfhearted

adj
  • Lacking full energy, effort, commitment, or resolve. 

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