impel vs put the frighteners on

impel

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

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

put the frighteners on

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