inure vs tone up

inure

verb
  • To cause someone to become accustomed to something that requires prolonged or repeated tolerance of one or more unpleasantries. 

  • To take effect, to be operative. 

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 inure and tone up occurred in a corpus of books? (source: Google Ngram Viewer )