anthem vs introitus

anthem

noun
  • A very popular song or track. 

  • A choral or vocal composition, often with a religious or political lyric. 

  • A hymn of praise or loyalty. 

verb
  • To celebrate with anthems. 

introitus

noun
  • A piece of music played before a mass; a musical introduction of any sort. 

  • The entrance to a hollow organ or canal; often specifically the entrance to the vagina. 

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