invigorate vs weaken

invigorate

verb
  • To heighten or intensify. 

  • To impart vigor, strength, or vitality to. 

  • To make lively. 

  • To give life or energy to. 

weaken

verb
  • To make weaker or less strong. 

  • To become weaker or less strong. 

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