A secret name; a name by which a person is known only to the initiated.

Code name; crypt or crypto for short, always capitalized. GT and CK prefixes to code names are used to identify the nature of the clandestine source. These two prefixes were both "diagraph" identifiers for the Soviet and East European program during this period. The diagraph is used in front of the cryptonym of the source as a more formal way of referring to the subject, not unlike putting "Mr." in front of "Smallwood."