bring to heel vs tone down

bring to heel

verb
  • To cause to act in a disciplined manner. 

  • To compel someone to obey; to force someone into a submissive condition. 

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 bring to heel and tone down occurred in a corpus of books? (source: Google Ngram Viewer )