brighten vs richen

brighten

verb
  • To make illustrious, or more distinguished; to add luster or splendor to 

  • To make more cheerful and pleasant; to enliven 

  • To grow bright, or more bright in color; to clear up 

  • To make bright or brighter in color. 

  • To become brighter or more cheerful in mood 

richen

verb
  • To become rich or richer; become superior in quality, condition or effectiveness. 

  • To make or render rich or richer. 

  • To gain richness; become heightened or intensified in brilliancy. 

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