intercession vs rogation

intercession

noun
  • A prayer to God on behalf of another person. 

  • The act of intervening or mediating between two parties. 

rogation

noun
  • A deeply serious and somber prayer or entreaty. 

  • The demand, by the consuls or tribunes, of a law to be passed by the people; a proposed law or decree. 

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