come up with vs stumble upon

come up with

verb
  • To manage to produce, deliver, or present (something) by inventing, creating, thinking of, or obtaining it. 

  • Used other than figuratively or idiomatically: see come, up, with. 

  • To reach or overtake. 

stumble upon

verb
  • To discover or find something by accident. 

  • To meet somebody by chance. 

How often have the words come up with and stumble upon occurred in a corpus of books? (source: Google Ngram Viewer )