outlawed vs unmentionable

outlawed

adj
  • put beyond the limits of the law, declared an outlaw or declared a criminal. 

  • put beyond the limits of the law, forbidden, against the law. 

unmentionable

adj
  • Not mentionable 

noun
  • Something not to be discussed in polite society. 

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