heap on vs vouchsafe

heap on

verb
  • To give someone a lot of something (advice, praise, insults, etc.), especially more so than they can handle or is appropriate 

vouchsafe

verb
  • To graciously give, to condescendingly grant a right, benefit, outcome, etc.; to deign to acknowledge. 

  • To receive or accept in condescension. 

  • To disclose or divulge. 

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