disallowed vs illicit

disallowed

adj

  • forbidden 

  • invalid 

illicit

adj

  • Unlawful. 

  • Breaking social norms. 

  • Not approved by law, but not invalid. 

noun

  • A banned or unlawful item. 

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