exordium vs postlude

exordium

noun
  • The introduction to an essay or discourse. 

  • A beginning. 

postlude

verb
  • To form a postlude (to); to end with a postlude. 

noun
  • A concluding passage of text or speech; an epilogue or afterword. 

  • The final part of a piece; especially music played (normally on the organ) at the end of a church service. 

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