ersatz vs unbelievable

ersatz

adj
  • Made in imitation; artificial, especially of a poor quality. 

noun
  • Something made in imitation; an effigy or substitute. 

unbelievable

adj
  • Implausible or improbable. 

  • Not to be believed. 

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

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