flee vs get blood out of a stone

flee

verb
  • To run away; to escape. 

  • To escape from. 

  • To disappear quickly; to vanish. 

get blood out of a stone

verb
  • To do something difficult, frustrating, or pointless. 

How often have the words flee and get blood out of a stone occurred in a corpus of books? (source: Google Ngram Viewer )