restrain vs step up

restrain

verb
  • To control or keep in check. 

  • To deprive of liberty. 

  • To strain again. 

  • To restrict or limit. 

step up

verb
  • To assume or take responsibility. 

  • To increase, augment, or advance, especially by one or more steps. 

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