downfall vs dry rot

downfall

noun
  • A precipitous decline in fortune; death or rapid deterioration, as in status or wealth. 

  • The cause of such a fall; a critical blow or error. 

  • An act of falling down. 

verb
  • To fall down; deteriorate; decline. 

dry rot

noun
  • Any progression of decay, corruption, or obsolescence. 

  • The crumbly, friable decayed portions of wooden members of buildings, especially at or below grade, usually caused by a fungal infection. 

  • A fungal infection which affects plants, in particular potatoes. 

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