ersatz vs substituend

ersatz

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

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

substituend

noun
  • A substitute; something that substitutes for another. 

  • A substituendum; something to be substituted or replaced. 

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