encourage vs weaken

encourage

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

  • To spur on, strongly recommend. 

  • To foster, give help or patronage 

weaken

verb
  • To become weaker or less strong. 

  • To make weaker or less strong. 

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