assist vs head off

assist

verb
  • To help compensate for what is missing with the help of a medical technique or therapy. 

  • To help. 

  • To make a pass that leads directly towards scoring. 

noun
  • A decisive pass made to the goal scorer 

  • A helpful action or an act of giving. 

  • A defensive play, allowing a teammate to record a putout. 

head off

verb
  • To avoid the undesirable consequences of; prevent. 

  • To start out. 

  • To intercept. 

  • To turn away from the wind. 

  • To begin moving away. 

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