rein in vs step up

rein in

verb
  • To stop or slow a horse by pulling the reins 

  • To stop or slow something, by exercising control. 

step up

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

  • To assume or take responsibility. 

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