rogation vs thanksgiving

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. 

thanksgiving

noun
  • A short prayer said at meals; grace, a benediction. 

  • An expression of gratitude. 

  • A public celebration in acknowledgement of divine favour. 

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