kickoff vs onfall

kickoff

onfall

noun
  • The fall of the evening. 

  • A fall of rain or snow. 

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

verb
  • To fall on or upon. 

  • To assault, attack. 

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