old hat vs rare

old hat

adj
  • Very familiar; common, hackneyed or out of date. 

rare

noun
  • A scarce or uncommon item. 

verb
  • To rear, bring up, raise. 

  • To rear, rise up, start backwards. 

adj
  • Thin; of low density. 

  • Very uncommon; scarce. 

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

  • Good; enjoyable. 

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