free speech vs restraint

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. 

restraint

noun
  • something that restrains, ties, fastens or secures 

  • control or caution; reserve 

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