fortify vs tone up

fortify

verb
  • To impart strength or vigor to. 

  • To increase the nutritional value of food by adding ingredients. 

  • To increase the defenses of; to strengthen and secure by military works; to render defensible against an attack by hostile forces. 

  • To add spirits to wine to increase the alcohol content. 

tone up

verb
  • To cause to give a higher tone or sound; to give a higher tone to; to make more intense; to heighten; to strengthen. 

  • To firm and strengthen the muscles of the body by regular exercise. 

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