few and far between vs unfrequent

few and far between

adj
  • Rare and scarce; hard to find. 

unfrequent

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

verb
  • To stop frequenting; cease to frequent. 

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