lighten vs lull

lighten

verb
  • To become less serious or more cheerful. 

  • 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 make brighter or clearer; to illuminate. 

  • To make light or lighter in weight. 

lull

verb
  • To become gradually calm; to subside; to cease or abate. 

  • To cause to rest by soothing influences; to compose; to calm 

noun
  • A period of rest or soothing. 

  • A period without waves or wind. 

  • An extended pause between sets of waves. 

  • A period of reduced activity; a respite 

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