extraordinary vs red-letter

extraordinary

adj
  • Remarkably good. 

  • Special or supernumerary. 

  • Not ordinary; exceptional; unusual. 

noun
  • Anything that goes beyond what is ordinary. 

red-letter

adj
  • Particularly significant or positive. 

How often have the words extraordinary and red-letter occurred in a corpus of books? (source: Google Ngram Viewer )