Gordian knot vs parable

Gordian knot

noun
  • The legendary knot tied to a pole near the temple of Zeus in Gordium. 

  • Any intricate and complex problem having a simple solution. 

parable

verb
  • To represent by parable. 

noun
  • A short narrative illustrating a lesson (usually religious/moral) by comparison or analogy. 

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