ersatz vs unsound

ersatz

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

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

unsound

adj
  • Not whole, not solid, defective. 

  • Infirm, diseased. 

  • Not good, unreliable. 

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