encourage vs head off

encourage

verb
  • To spur on, strongly recommend. 

  • To mentally support; to motivate, give courage, hope or spirit. 

  • To foster, give help or patronage 

head off

verb
  • To start out. 

  • To intercept. 

  • To avoid the undesirable consequences of; prevent. 

  • To turn away from the wind. 

  • To begin moving away. 

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