dehancement vs retrogradation

dehancement

noun
  • Deterioration, decline, reduction. 

retrogradation

noun
  • Decline, degradation. 

  • A reaction that takes place in gelatinized starch when the amylose and amylopectin chains realign themselves, largely responsible for bread becoming stale. 

  • Motion in a retrograde manner. 

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