hymn vs introitus

hymn

noun
  • A song of praise or worship, especially a religious one. 

verb
  • To praise or extol in hymns. 

  • To sing a hymn. 

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 hymn and introitus occurred in a corpus of books? (source: Google Ngram Viewer )