impede vs impel

impede

verb
  • To get in the way of; to hinder. 

impel

verb
  • To drive forward; to propel an object, to provide an impetus for motion or action. 

  • To urge a person; to press on; to incite to action or motion via intrinsic motivation. 

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