unfrequent vs unwonted

unfrequent

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

verb
  • To stop frequenting; cease to frequent. 

unwonted

adj
  • Not customary or habitual; unusual; infrequent; strange. 

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