Translation guide
A code name is a substitute name used to conceal identity, project, or operation. In Japanese, the most common equivalent is コードネーム, a direct loanword. Other options include 暗号名 (formal, military) and 秘匿名 (rare, literary).
コードネームは何ですか？
What is the code name?
A name used to hide the real identity of a person, project, or operation.
The most common and neutral term, used in business, military, and casual contexts. A direct loanword from English.
このプロジェクトのコードネームは「サンライズ」です。
The code name for this project is 'Sunrise'.
Literally 'cipher name'. More formal and often used in military or intelligence contexts. Can sound technical.
そのスパイの暗号名は「ナイトフォール」だった。
The spy's code name was 'Nightfall'.
A rare, literary term meaning 'secret name'. Not commonly used in everyday speech.
彼は秘匿名で活動していた。
He operated under a code name.
コードネーム is widely understood and can be used in most situations. For formal documents or military contexts, 暗号名 may be more appropriate. Avoid 秘匿名 unless you are writing a novel or historical text.
この作戦のコードネームは「オペレーション・ブルー」です。
The code name for this operation is 'Operation Blue'.