A code name is a word or phrase used to refer secretly to a specific person, group, project, or plan of action. Individual spies and large-scale military operations are often referred to by code names to protect their identity. For example, the code name for the United States' project to produce an atomic bomb during World War II was "Manhattan Project," the codename for the U.S. plan to invade Okinawa on April 1, 1945 was "Iceberg," the Nazi German plan to invade England had the code name "Operation Sea Lion," and the code name of Spanish double agent Juan Pujol Garcia, who spied for the British while pretending to spy for the Nazis, was "Garbo." So common is the use of code names that an entire book has been devoted to cataloguing the code names used during World War II.
A code name is a particular type of code word. A code word is any word or phrase that has been chosen to signify a specific message while keeping that message hidden from a third party. Functional codes may contain thousands of code words, some of which may also be code names; however, a code name need not be part of a larger code. It may, in effect, be a code unto itself, comprised of only one word.
█ FURTHER READING:
Chant, Christopher. The Encyclopedia of Codenames of World War II. London: Routledge & Kegan Paul, 1986.
Churchouse, Robert. Codes and Ciphers. Cambridge, UK: Cambridge University Press. 2002.
Mollin, Richard A. An Introduction to Cryptography. New York: Chapman & Hall 2001.
Singh, Simon. The Code Book. New York: Doubleday, 1999.