declaration of war vs lull

declaration of war

noun
  • A formal announcement by a country or other body with military capability that it is in a state of war with another such entity. 

lull

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

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

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 declaration of war and lull occurred in a corpus of books? (source: Google Ngram Viewer )