castaway vs might-have-been

castaway

noun
  • A discarded person or thing. 

  • An outcast; someone cast out of a group or society. 

  • A shipwrecked sailor. 

adj
  • Cast adrift or ashore; marooned. 

  • Shipwrecked. 

  • Cast out; rejected or excluded from a group. 

might-have-been

noun
  • Someone or something whose potential greatness was not achieved. 

How often have the words castaway and might-have-been occurred in a corpus of books? (source: Google Ngram Viewer )