clemency vs exculpation

clemency

noun
  • A pardon, commutation, or similar reduction, removal, or postponement of legal penalties by an executive officer of a state. 

  • The gentle or kind exercise of power; leniency, mercy; compassion in judging or punishing. 

exculpation

noun
  • The act of exculpating from alleged fault or crime. 

  • That which exculpates; an excuse. 

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