break free vs head for the hills

break free

verb
  • To liberate oneself; to free oneself; to become free (from or of something or someone). 

head for the hills

verb
  • To go to a safe place; to seek refuge; to flee. 

  • To travel to a higher elevation, especially to a rural region on vacation. 

How often have the words break free and head for the hills occurred in a corpus of books? (source: Google Ngram Viewer )