Engine for the Neutralizing of Information by the Generation of Miasmic Alphabets
Device invented by Leonard of Quirm to encrypt and decrypt messages, around the time of the crowning of the dwarf Low King, when politicians, diplomats, and spies were busy from Überwald outward all across the main continent. This Engine looks like a typewriter with strangely arranged arms, many of which bear not letters but symbols. The Engine has a very long name because Leonard has never been good at naming his inventions, but if Ankh-Morporkians are ever interested in using acronyms, the acronym for the Engine would have been ENIGMA. Must be a coincidence.
Appears in: The Fifth Elephant.
During WW2, the standard cryptographical device used by the German Wehrmacht was called the Enigma machine. The Germans fondly thought it was impregnable. But first the Poles - who had a very big interest in finding out what their western neighbour intended militarily - found ways of cracking its randomly generated ciphers. Since this only confirmed what they already suspected - ie, that they were going to be invaded - following the brief war, the Polish code-breakers got to Britain with what they knew. The British then devoted a whole industry to cracking Enigma, a by-product of which was the world's first working computer and the remotest ancestor of the machine on which you are reading this.
Even though the description of Leonardo's machine is suspiciously similar to the German Enigma, it's probably just coincidence...
It is also the case that the real Roundworld Leonardo da Vinci also had an interest in codes and cryptography. In fact, Dan Brown makes a big thing of this in "The da Vinci Code", his best-selling potboiler. A machine, not unlike a pre-electricity Enigma device, that da Vinci called the "cryptex" features largely in that book.