bilboes vs incarceration

bilboes

noun
  • An iron bar fitting around the ankles of prisoners, and having sliding shackles. 

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 bilboes and incarceration occurred in a corpus of books? (source: Google Ngram Viewer )