free speech vs imprisonment

free speech

noun
  • The right to express an opinion in public without being restrained or censored. 

  • Expressions that are or should be allowed in some moral or legal context. 

imprisonment

noun
  • A confinement in a place, especially a prison or a jail, as punishment for a crime. 

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