amnesty vs have mercy on

amnesty

verb
  • To grant a pardon (to a group) 

noun
  • Forgetfulness; cessation of remembrance of wrong; oblivion. 

  • An act of the sovereign power granting oblivion, or a general pardon, for a past offense, as to subjects concerned in an insurrection. 

have mercy on

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