counterfactual vs unbelievable

counterfactual

adj
  • Contrary to known or agreed facts; untrue. 

  • Of or in comparison to a hypothetical state of the world. 

noun
  • A conditional statement in which the conditional clause is false. 

  • A claim, hypothesis, or other belief that is contrary to the facts. 

  • A hypothetical state of the world, used to assess the impact of an action. 

unbelievable

adj
  • Not to be believed. 

  • Amazing, incredible; so surprising it is almost unable to believe. 

  • Implausible or improbable. 

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