litany vs petition

litany

noun
  • A ritual liturgical prayer in which a series of prayers recited by a leader are alternated with responses from the congregation. 

  • A prolonged or tedious list. 

petition

noun
  • A prayer; a supplication; an entreaty. 

  • A compilation of signatures built in order to exert moral authority in support of a specific cause. 

  • A formal written request for judicial action. 

  • A formal, written request made to an official person or organized body, often containing many signatures. 

verb
  • To make a request to, commonly in written form. 

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