A code name is a secret name used to refer to a name, word, project or person. Spies are often referred to by their code name to make discovery more difficult. Code names may also be used in industrial espionage to protect secrets  from business rivals. 
Secrecy is not the only reason for their use. Standard words and phrases are easier to hear on radio channels like walkie-talkies.
Code names became numerous in World War II. Names like Operation Barbarossa and Operation Overlord and the Manhattan Project became famous.
References
| Personal names and anthroponymy (or the study of the proper names of human beings) | 
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| Personal name |  | 
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| By trait |  | 
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| By life situation |  | 
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| Pseudonyms (list) |  | 
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| By culture Surnames by country
 | | East Asian |  | 
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 | Muslim world and Western Asia
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AfghanArabicAzerbaijaniBengaliMandaeanPakistaniPashtunPersianSindhiSomaliTatarTurkish
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 | Oceania | 
Australian AboriginalFijianHawaiianMāori
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 | Sub-Saharan Africa | 
AshantiDemocratic Republic of the CongoEthiopian and EritreanEweGhanaianIgboYorubaZimbabwean
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 | Europe, North America and Australasia
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AlbanianArmenianAshkenazi JewishBasqueCeltic
CornishIrishManxScottishWelsh
FinnishFrenchGeorgianGermanic
DutchEnglish
AmericanAfrican-AmericanCanadianHongkongese
GermanGothicIcelandicScandinavian
Greek
HungarianItalianKalmykLatvianLithuanianPortugueseRoman
PraenomenNomenCognomenAgnomen
RomanianSlavic
BulgarianCroatianCzechEastern Slavic
BelarusianRussianUkrainian
MacedonianPolishSerbianSlovakSuffixes
Spanish
Sakha
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 | Indosphere (South Asia and Southeast Asia)
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BalineseBurmeseFilipinoIndonesian
JavaneseCambodianMalaysianIndian
LaoSinhaleseThai
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| By religion | 
Christian name
Buddhist surnameDharma nameJewish name
Mandaean nameTheophoric name
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| Manners of address List
 of authority/of honour
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Honorific
DiplomaticImperial, royal, and nobleJudiciaryReligious
Pre-nominal lettersSuffix
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 | Titles |  | 
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