(first) appearance vs commencement

(first) appearance

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. 

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