commencement vs prelude

commencement

noun
  • The first existence of anything; act or fact of commencing; the beginning. 

  • The day when degrees are conferred by colleges and universities upon students and others. 

  • A graduation ceremony, from a school, college or university. 

prelude

noun
  • An introductory or preliminary performance or event. 

  • A forerunner to anything. 

  • A standard module or library of subroutines and functions to be imported, generally by default, into a program. 

  • A short, free-form piece of music, originally one serving as an introduction to a longer and more complex piece; later, starting with the Romantic period, generally a stand-alone piece. 

verb
  • To play an introduction or prelude; to give a prefatory performance. 

  • To introduce something, as a prelude. 

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