diminish vs tone down

diminish

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

  • To taper. 

  • To disappear gradually. 

  • To take away; to subtract. 

  • To make smaller. 

  • To become less or smaller. 

tone down

verb
  • To moderate or relax; to diminish or weaken the striking characteristics of; to soften. 

  • To make a television program, piece of writing, etc. less offensive and so more suitable for a family audience. 

  • To relax; to make quieter or less obtrusive; to make milder. 

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