cheapen vs diminish

cheapen

verb
  • to decrease the value of; to make cheaper 

  • to become cheaper 

  • to make vulgar 

diminish

verb
  • To become less or smaller. 

  • To taper. 

  • To disappear gradually. 

  • To take away; to subtract. 

  • To make smaller. 

  • To lessen the authority or dignity of; to put down; to degrade; to abase; to weaken; to nerf (in gaming). 

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