spring out vs unfold

spring out

verb
  • To emerge or arise. 

  • Used other than figuratively or idiomatically: see spring, out. 

  • To break out; to escape. 

  • To spend the season of spring in outdoor pursuits such as camping. 

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 spring out and unfold occurred in a corpus of books? (source: Google Ngram Viewer )