unfold vs unravel

unfold

verb
  • To undo a folding. 

  • To release from a fold or pen. 

  • To turn out; to happen; to develop. 

  • 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. 

unravel

verb
  • To become undone; to collapse. 

  • To separate the threads (of); disentangle. 

  • To become separated; (of something woven, knitted, etc.) to come apart. 

  • To separate the connected or united parts of; to throw into disorder; to confuse. 

  • To clear from complication or difficulty; to unfold; to solve. 

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