rare vs unforgettable

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. 

verb
  • To rear, bring up, raise. 

  • To rear, rise up, start backwards. 

noun
  • A scarce or uncommon item. 

unforgettable

adj
  • Very difficult or impossible to forget. 

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