illumine vs lighten

illumine

verb
  • To become bright; to light up. 

  • To cause (the eyes) to see. 

  • To enlighten intellectually. 

  • To cause (something) to glow or shine with light. 

  • To enlighten (someone) spiritually; to induce (someone) to adopt, or believe in the truth of, a religion, religious tenet, etc. 

  • To enlighten (someone) intellectually. 

  • To decorate (a page of a manuscript book) with ornamental designs. 

  • To shine light on (something). 

  • To cause (a person or their face) to show enlightenment, happiness, etc. 

  • Of a person or their face: to show enlightenment, happiness, etc. 

lighten

verb
  • To make brighter or clearer; to illuminate. 

  • To become light or lighter in weight. 

  • To become brighter or clearer; to brighten. 

  • To make less serious or more cheerful. 

  • To illuminate with knowledge; to enlighten. 

  • To descend; to light. 

  • To emit or disclose in, or as if in, lightning; to flash out, like lightning. 

  • To alleviate; to reduce the burden of. 

  • To become less serious or more cheerful. 

  • To make light or lighter in weight. 

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