dampen vs strengthen

dampen

verb
  • To become damped or deadened. 

  • To lessen; to dull; to make less intense (said of emotions and non-physical things). 

  • To become damp or moist. 

  • To make damp or moist; to make moderately wet. 

strengthen

verb
  • To augment; to improve; to intensify. 

  • To make strong or stronger; to add strength to; to increase the strength of; to fortify. 

  • To empower; to give moral strength to; to encourage; to enhearten. 

  • To reinforce, to add to, to support (someone or something) 

  • To grow strong or stronger. 

  • To substantiate; to corroborate (a belief, argument, etc.) 

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