exculpation vs purgation

exculpation

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

  • That which exculpates; an excuse. 

purgation

noun
  • The process or act of cleansing from sin or guilt. 

  • The process or act of purging, such as by the use of a purgative. 

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