develop vs unfold

develop

verb
  • To change with a specific direction, progress. 

  • To progress through a sequence of stages. 

  • To bring out images latent in photographic film. 

  • To advance; to further; to promote the growth of. 

  • To acquire something usually over a period of time. 

  • To place one's pieces actively. 

  • To create. 

  • To cause a ball to become more open and available to be played on later. Usually by moving it away from the cushion, or by opening a pack. 

  • To change the form of (an algebraic expression, etc.) by executing certain indicated operations without changing the value. 

unfold

verb
  • To turn out; to happen; to develop. 

  • To undo a folding. 

  • To release from a fold or pen. 

  • To open (anything covered or closed); to lay open to view or contemplation; to bring out in all the details, or by successive development. 

  • To reveal. 

noun
  • In functional programming, a kind of higher-order function that is the opposite of a fold. 

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