loosen vs relax

loosen

verb
  • To become loose. 

  • To make loose. 

  • To free from restraint; to set at liberty. 

  • To become unfastened or undone. 

  • To relieve (the bowels) from constipation; to promote defecation. 

  • To disengage (a device that restrains). 

relax

verb
  • 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. 

  • To become more lenient. 

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