allegation vs exculpation

allegation

noun
  • The act of alleging. 

  • An assertion, especially an accusation, not necessarily based on facts. 

exculpation

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

  • That which exculpates; an excuse. 

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