grind down vs rot

grind down

verb
  • To weaken someone's morale over a long period. 

  • To make something hard smaller and smoother by gradually rubbing off tiny bits, to wear down. 

rot

verb
  • To spend a long period of time (in an unpleasant place). 

  • To expose, as flax, to a process of maceration, etc., for the purpose of separating the fiber; to ret. 

  • To suffer decomposition due to biological action, especially by fungi or bacteria. 

  • To decline in function or utility. 

  • To (cause to) deteriorate in any way, as in morals; to corrupt. 

  • To make putrid; to cause to be wholly or partially decomposed by natural processes. 

noun
  • Any of several diseases in which breakdown of tissue occurs. 

  • The process of becoming rotten; putrefaction. 

  • Verbal nonsense. 

  • Decaying matter. 

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