flee vs run away

flee

verb
  • To run away; to escape. 

  • To escape from. 

  • To disappear quickly; to vanish. 

run away

verb
  • To flee by running. 

  • To leave home, or other place of residence, usually unannounced, or to make good on a threat, with such action usually performed by a child or juvenile. 

  • To become a runaway. 

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