frequent vs unfrequent

frequent

adj
  • Done or occurring often; common. 

  • Occurring at short intervals. 

  • Addicted to any course of conduct; inclined to indulge in any practice; habitual; persistent. 

verb
  • To visit often. 

unfrequent

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

verb
  • To stop frequenting; cease to frequent. 

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