scarce vs unfrequent

scarce

adj
  • Uncommon, rare; difficult to find; insufficient to meet a demand. 

unfrequent

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

verb
  • To stop frequenting; cease to frequent. 

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