When a person, or a secret project, is well known under a codename, why not use that for the title? And due to where codenames usually pop up, Spy Fiction works are the usual subject of this trope.
Sometimes how Protagonist Title-type Superhero comic books are done. And rare but obvious cases put the word "Codename" right in the title!
Possibly a Double-Meaning Title, which is only for titles with multiple meanings relevant to the work.
But it often overlaps with Event Title, The Place, Character Title, or MacGuffin Title, for being something that happens or will happen, a place, someone, or something.
Usually a type of Spy Speak.
Examples
- Codename: Sailor V: Protagonist Title for a Sailor Fuku-ed Magical Girl with a theme of Venus, both planet and goddess.
- Cyborg 009: The nine Cyborgs are given numerical codenames from 001-009, when transformed into living weapons.
- Codename Knockout was a comic from Vertigo Comics which ran for 24 issues. It followed the adventures of buxom blonde Angela St. Grace (the "Codename: Knockout" of the title) a secret agent and operative for the "G.O.O.D." (Global Organization for the Obliteration of Dastardliness) organization as she battled the nefarious agents of "E.V.I.L." (Extralegal Vendors of Iniquity and Licentiousness).
- X23: Codenamed for being Sarah's 23rd attempt to create a female clone, a.k.a having the X chromosome instead of a male / Y chromosome)
- Code Name: Diamond Head: Protagonist Title-type Spy Fiction, named after the place in Hawaii.
- Ice Station Zebra: An action-adventure film from 1968. The Place of the title refers to the destination an American submarine is ordered to visit, under a cover story of aiding Russians. The captain discovers his passengers have another agenda. Based on the novel by Archibald MacLean.
- The Little Drummer Girl: Job Title, also a Protagonist Title for the young woman who assists a spy agency.
- Three Days of the Condor is a 1975 political thriller film in which the protagonist is a CIA spy code named Condor.
- Undercover Brother: Spy Protagonist Title.
- Valkyrie is about the titular operation, the Nazi government's contingency plan which has been secretly co-opted by a group of conspirators who plan to force it into effect by assassinating Hitler so they can launch a coup.
- The Choose Your Own Adventure book Your Code Name Is Jonah casts the reader as a spy using the code name Jonah. The spy is investigating a missing scientist who was researching whale songs.
- Codename Villanelle: Spy Fiction with Protagonist Title. Real name, Oxana Borisovna Vorontsova, and is an Omnibus, Named After First Installment.
- The Day of the Jackal has the disgruntled OAS hire a professional assassin to subtract French President Charles de Gaulle. The assassin chooses the codename "jackal" upon accepting the mission. When British Intelligence is contacted via the "old boy network," they posit that a mercenary named Charles Calthrop might be the assassin.
Brit: The French word for jackal is chacal, I believe. Well, if you take the first three letters of Charles, and the first three letters of Calthrop...
- The Little Drummer Girl: Also a Protagonist Title for the young woman who assists a spy agency.
- The Man Who Was Thursday: "Thursday" is the code name for one of the seven leaders of a Bomb Throwing Anarchist organization, who each have a "Day of the Week" Name. The head of the group is Sunday.
- The Proteus Operation: The mission to the past is given the code name Operation Proteus.
- The earlier Quiller novels had Mad Lib Thriller Titles. This changed with "Northlight", after which every novel was titled "Quiller (name)". The real name of the protagonist is never revealed; Quiller is just his code name which members of The Bureau use when referring to him, while Quiller uses whatever cover name he's been given on a mission.
- Legion is a supervillain Protagonist Title.
- The Little Drummer Girl: Also a Protagonist Title for the young woman who assists a spy agency.
- Quantico did this for its second season's episodes, with the titles in BLOCK CAPITALS, such as "LIPSTICK", which was something about spying in Mexico City.
- Walker, Texas Ranger did this for the fifth season episode "Codename: Dragonfly", whereupon Walker takes on a old nemesis from the Vietnam war who stole the titular multimillion-dollar military helicopter to transport drugs for the cartels.
- Codename: ICEMAN: The title is taken from the name of a covert operation to rescue a U.S. ambassador from terrorists that Westland goes on.
- Codename MAT: A "mammoth space arcade strategy epic" on the ZX Spectrum. A 3D Space Shoot 'Em Up with tactical and strategic elements where the player defended the solar system from the invading Myons. The name MAT was an acronym for Mission: Alien Termination.
- Codename Steam: The title group (the acronym stands for Strike Team Eliminating the Alien Menace) is a squad of literary characters like Tom Sawyer, Princess Tiger Lily, and The Cowardly Lion battling alien invaders.
- Codename: Tenka, also a Protagonist Title for the main character, Joseph D. Tenka.
- Hitman: Codename 47: The title comes from the "name" of the main protagonist, a genetically-engineered assassin known only by his serial number, 47.
- Katana ZERO: The title references the codename of "Subject Zero", making it a Protagonist Title, and who was the first person tested for the perception-enhancing combat drug Chronos.
- Metal Gear Solid 3: Snake Eater features Operation Snake Eater. The goal was for Naked Snake to assassinate the founding member of the Cobra Unit, The Boss, and to destroy Sokolov's nuclear carrying weapon. At least that's what Snake's officials told him as more of the story unfolds.
- Code Name: Hunter by Darc Sowers, a Furry comic about covert agents in Britain charged with containing and controlling magic powers that have been loosed in London.
- Codename: Kids Next Door: Blatant about it, and uses this for Fun with Acronyms-type Idiosyncratic Episode Naming with acronyms relating to the plot, such as:
- C.A.K.E.D: Capturize And Kidnapify Enemy Dessert.
- G.H.O.S.T stands for "Ghostly Hamsters Overwhelm Spooky Treehouse"
- L.U.N.C.H is "Lizzie Underappreciates Nigel's Chowtime Hardworkingness"
- Danger Mouse: Secret Agent Protagonist Title, named as a reference to Danger Man.