nonhuman vs unbelievable

nonhuman

adj
  • Not human; not of the human race. 

noun
  • A creature or thing that is not human. 

unbelievable

adj
  • Not to be believed. 

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

  • Implausible or improbable. 

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