impoverish vs step up

impoverish

verb
  • To make poor. 

  • To become poor. 

  • To weaken in quality; to deprive of some strength or richness. 

step up

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

  • To assume or take responsibility. 

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