chorale vs introitus

chorale

noun
  • A form of Lutheran or Protestant hymn tune. 

  • A chorus or choir. 

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