invigorate vs light a fire under

invigorate

verb
  • To heighten or intensify. 

  • To impart vigor, strength, or vitality to. 

  • To make lively. 

  • To give life or energy to. 

light a fire under

verb
  • To motivate or encourage (someone) to start sooner or move faster. 

How often have the words invigorate and light a fire under occurred in a corpus of books? (source: Google Ngram Viewer )