free rein vs incarceration

free rein

noun
  • Loose rein(s), as of a horse. 

  • The absence of constraints; freedom to make decisions. 

incarceration

noun
  • The act of confining, or the state of being confined; imprisonment. 

  • A constriction of the hernial sac, rendering it irreducible, but not great enough to cause strangulation. 

How often have the words free rein and incarceration occurred in a corpus of books? (source: Google Ngram Viewer )