enhance vs weaken

enhance

verb
  • To augment or make something greater. 

  • To take up contrast agent (for an organ, tissue, or lesion). 

  • To improve something by adding features. 

  • To be raised up; to grow larger. 

weaken

verb
  • To make weaker or less strong. 

  • To become weaker or less strong. 

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