cryptonym

• A code name or cryptonym is a word or name used clandestinely to refer to another name or word, in order to protect secret projects and the like from business rivals. —  xml's Blinklist.com
• I am not a Thackeray reader, alas, but thought HogPro readers might be as interested as I was in this potential hat-tip and key to the Gaunt family cryptonym as well as a pointer to the 'Dark Mark' of Voldemort. —  HogwartsProfessor.com
• [12] It is considered especially elegant if the digraph is part of the word, so if the digraph for "Eastasia" were EA, EASTWOOD would be a perfectly acceptable cryptonym. clandestine cell system. —  Citizendium, the Citizens' Compendium - Recent changes [en]
• If you don't mind my parsing the cryptonym, the habit of every Potter reader, —  HogwartsProfessor.com
• Tartar was only a cryptonym by which heretics knew each other, and adds: _Il n'y a donc pas trop à s'etonner des noms bizarres de —  Among My Books Second Series

Allen's Synonyms and Antonyms