relax vs step up

relax

verb
  • To become more lenient. 

  • To become loose. 

  • To become less severe or tense. 

  • To make something (such as codes and regulations) more lenient. 

  • To calm down. 

  • To relieve (something) from stress. 

  • To make something less severe or tense. 

  • To make something loose. 

step up

verb
  • To assume or take responsibility. 

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

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