commencement vs onfall

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. 

onfall

noun
  • A falling on or upon; an attack, onset, or assault. 

  • The fall of the evening. 

  • A fall of rain or snow. 

verb
  • To fall on or upon. 

  • To assault, attack. 

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