admonish vs rap over the knuckles

admonish

verb
  • To inform or notify of a fault; to rebuke gently or kindly, but seriously; to tell off. 

  • To advise against wrongdoing; to caution; to warn against danger or an offense. 

  • To instruct or direct. 

rap over the knuckles

How often have the words admonish and rap over the knuckles occurred in a corpus of books? (source: Google Ngram Viewer )