encourage vs oblige

encourage

verb
  • To foster, give help or patronage 

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

  • To spur on, strongly recommend. 

oblige

verb
  • To do (someone) a service or favour (hence, originally, creating an obligation). 

  • To be indebted to someone. 

  • To constrain someone by force or by social, moral or legal means. 

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