possibility vs unlikelihood

possibility

noun
  • A thing possible; that which may take place or come into being. 

  • The quality of being possible. 

  • An option or choice, usually used in context with future events. 

unlikelihood

noun
  • Absence of likelihood; the state of being unlikely or improbable; improbability. 

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