toss-up vs unlikelihood

toss-up

noun
  • A decision in which neither choice is clearly favorable or unfavorable, or for which the outcome does not matter. 

  • Either of two outcomes that are equally likely. 

  • The toss of a coin used to decide some issue. 

unlikelihood

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

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