rare vs unfrequent

rare

adj
  • Very uncommon; scarce. 

  • Thin; of low density. 

  • Particularly of meat, especially beefsteak: cooked very lightly, so the meat is still red. 

  • Good; enjoyable. 

noun
  • A scarce or uncommon item. 

verb
  • To rear, bring up, raise. 

  • To rear, rise up, start backwards. 

unfrequent

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

verb
  • To stop frequenting; cease to frequent. 

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