onfall vs onrush

onfall

verb
  • To assault, attack. 

  • To fall on or upon. 

noun
  • The fall of the evening. 

  • A fall of rain or snow. 

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

onrush

verb
  • To assault aggressively. 

  • To rush or flow forward forcefully. 

noun
  • An aggressive assault. 

  • A forceful rush or flow forward. 

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