desultory vs unfrequent

desultory

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

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

  • Disappointing in performance or progress. 

unfrequent

adj
  • Not frequent; not common; not happening often; infrequent. 

verb
  • To stop frequenting; cease to frequent. 

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