Language serves as a means of communication. Yet, there have always been people who did not want everyone to understand them. As a result, they developed secret languages. In his book, Daniel Heller-Roazen takes a journey through the history of artificial and secret languages. From the languages of crooks and sacred languages to the great linguist Ferdinand de Saussure's engagement with anagrams, from the arcane linguistic art of druids and Bible scribes to Tristan Tzara, who co-founded the Dada movement and later attempted to decipher the songs of Villon, Heller-Roazen explores the linguistic art of tricksters and puzzle enthusiasts, showing that these languages, which play sound and meaning against each other, are more connected to poetry than previously thought.