Then, this can mean they want to be rid of you, or exploit you, and there is the little matter of figuring out who would understand if you say it. Heaven help you if you accidentally learned it; you will find yourself knee-deep in trouble before you can blink.
In The Infiltration, it is a frequent point of failure — but if you do have the knowledge, it lets you in entirely. The Ancient Tradition, Ancient Conspiracy, and Ancient Order of Protectors take it very seriously.
Unlike Only Smart People May Pass, you can not figure this one out from the clues; you have to have learned it. (Occasionally, the Genius can manage to figure it out, but it will always take them serious time and effort.) This is, if they did it right. Sometimes they were clumsy. Conversely, an Only Smart People May Pass riddle may turn into this if the answer is too insane or difficult.
Compare Trust Password, Only the Worthy May Pass, Only the Pure of Heart, Only Good People May Pass. If it's something only a specific person would know or say, that's Trust Password or Something Only They Would Say.
- The Case Files of Jeweler Richard likes this trope.
- Saul tests Seigi's knowledge of gemstones with Richard's acrostic ring to ensure he cares enough to pay attention to Richard's lectures as see his potential as a jeweler apprentice.
- Richard leaves a Trail of Bread Crumbs for Seigi with clues from conversations they had previously about gemstones.
- In volume nine, Vincent asks Seigi everything he knows about coral as a gemstone before giving him information.
- In volume ten, Octavia sets up a riddle game with Seigi and Richard to test Seigi's knowledge of gemstones and Richard's knowledge of ancient Japanese literature.
- In Winter War, while meeting in an occupied city, Soi Fong and one of her Onmitsukidou use lines from a Tang Chinese poem as a password, switching off in the middle of lines and then skipping to the end. While someone sufficiently learned might know the poem, they probably wouldn't know when to switch off, or recognize what was going on based on the first phrase.
Kage: After battle...
Soi Fong: Many new ghosts cry. The solitary old man...
Kage: ...worries and grieves. [pause] To many places, communication is lost. I sit straight at my desk but cannot read my books for grief.
- The Lumberjack and the Tree-Elf the first installment in the The Victors Project series has this Mack takes Jason to a rebel meeting at the home of Mayor Lourdes and his family.
Carla Lourdes: The days are dark.Mack: I brought a lantern.
- Crossed Lines: Yamato earns Denjiro's trust because she knows about Toki's Devil Fruit powers, something obscure enough to convince him she genuinely read Oden's journal.
- In Tangled, the guard captain is tweaked with demands for a password during the rescue.
Shorty: What's the password?
Shorty: Nope! [closes hatch]
Captain: OPEN THIS DOOR!!!
Shorty: Not even close!
- In Frankenstein The College Years, Doctor Lipzigger's computer security demands, in addition to a keycard he bequeathed to the protagonist duo, the answers to two questions: One about chemistry, the other about Star Trek. It was meant so that only the protagonists may unlock it, together.
- In Airheads, Chazz confronts Chris Moore, who claims he's a music executive, but Chazz thinks he's really a cop, so he asks him "Whose side did you take in the Van Halen/Roth split, Van Halen or Roth?" When Moore answers "Van Halen", he's immediately accused of being a cop, but he asks for another chance. So Chazz asks "Who would win a wrestling match, Lemmy or God?" Moore initially answers "Lemmy", but when Chazz imitates a buzzer, he changes his answer to "God", before Rex yells "Wrong, dickhead, trick question, Lemmy is God!", and Moore is forced out.
- In Back to the Future Part II, the old Biff Tannen of 2015 gains the trust of the young Biff of 1955 by starting his car in a way only he knows about.
- In Monty Python and the Holy Grail, "Who approaches the Bridge of Death must answer me These Questions Three..., 'ere the other side he see." The first two are always "What is your name?" and "What is your quest?", but the third one is the one that can stump people whether it's "What is the capital of Assyria?" or "What is the airspeed velocity of an unladen swallow?"
- In That Thing You Do!, Guy asks the hotel doorman Lamarr for the name of a good jazz club in town. Lamarr won't reveal it until he is certain that Guy knows his stuff.
Lamarr: Oh, you want good jazz? Good jazz? Lemme ask you a question. Who played cornet for Jacques St. Claire on "Vital Stats"?
Guy: Scottie McDonald.
Lamarr: Get in the cab. Get in the cab! [to the driver] Take this young man to the Blue Spot.
- In The Angel Levine, Morris asks Levine to prove he's Jewish by reciting a Hebrew table blessing, which he does easily.
- In Guards! Guards!, The Elucidated Brethren of the Ebon Night have a long string of passwords (as does every other secret society in the area, oddly enough at least some of them have the same ones, meaning they have to help each other's members to the right meeting place).
- Dune: Lady Jessica is able to gain acceptance among the Fremen by using phrases planted in their culture by the Missionaria Protectiva (which manipulates religious beliefs to benefit the Bene Gesserit).
- In Harry Potter, students in Hogwarts need a password to enter their dormitories. (With the exception of the students in Ravenclaw, who use a riddle — Only Smart People May Pass.)
- Doubly subverted in Septimus Heap, since while the DoorKeeper of the House of Foryx doesn't allow Jenna and Beetle to enter even after they have resolved the puzzle that is The Right of The Riddle, they eventually get into the house with violence.
- The Kaiel Death Rite, in Courtship Rite, which is applied to heretics, consists of seven increasingly difficult deadly tests. Each test must be designed so that someone who is familiar with "the common wisdom" can pass, because it is the common wisdom that is threatened by heresy. When the protagonists are ordered to marry Oelita, the Gentle Heretic, they decide to use the Death Rite to test her fitness to wed them.
- In Rick Riordan's The Heroes of Olympus novel The Mark Of Athena, the ghosts of Mithritic initiates think they have this. Annabeth does indeed have some of their secret knowledge, but bluffs through the rest, notably added by her ability to make guesses based on the room's decor.
- In Dan Abnett's Bequin novel Pariah, Lupan tries to make a veiled approach to Beta. Unfortunately for him, the code terms he used were so ineptly woven in as to signal that something was wrong to her.
- Inverted in Illuminatus!. Robert Drake spends a considerable amount of time and effort trying to force his way into The Illuminati by demonstrating his knowledge of the Ancient Conspiracy.
- In a short story note , the villain steals art carvings and tries to sell them as his own work. The original sculptor takes him to court, where a judge orders them each to carve an image as he watches. The plagiarist's work is obviously much worse, so he is found out.
- The Lord of the Rings: When the Fellowship goes to the Dwarvish mines of Moria, Gandalf finds the doors with an Elvish inscription: "The Doors of Durin, Lord of Moria. Speak, friend, and enter.". So, he tries speaking an Elvish phrase, but when that doesn't work, he tries several others before giving up. That's when Frodo realizes that the password is the Elvish word for friend, "mellon" and it opens. However, they soon see that all the dwarves have long since been slain by orcs.
- In Doctor Who, when the Doctor meets up with the amnesiac Brigadier, teaching at a boys' school, the Brigadier's attitude undergoes an abrupt change when the Doctor mentions UNIT — he still doesn't know him, but anyone with sufficient secret clearance to mention it ought to know better than to talk like that.
- On No Ordinary Family JJ proves he belongs in the Smart People's Club by citing its latitude & longitudinal coordinates.
- Pops up repeatedly in the last two seasons of Stargate SG-1. In order to access the ancient treasure in "Avalon", one must possess "wealth of knowledge and truth of spirit." Similarly, "wisdom" is one of the virtues required to find the Sangraal in the season 10 two-parter "The Quest". In both cases, the protagonists are required to not only solve puzzles and riddles, but also have prior knowledge of Ancient language and culture (and Arthurian Legend).
- The Magicians (2016): Only humans from Earth can become the kings and queens of Fillory, so the Knight of Crowns has to test aspirants to be sure they're telling the truth. He does so using bizarre pop culture questions from the '90s. ("Is it not the '90s on Earth?") Eliot ultimately wins the crown of High King by reciting Patrick Swayze's speech from Dirty Dancing.
Knight: What was the hit song made by the children of famous actors?
Margo: ...dude. That's hella vague.
- Betrayal at Krondor has a great many chests called "Wordlocks" that are essentially combination locks with letters instead of numbers, and they have riddles on them. The answer to the riddle is the combination, so most of these follow a different trope, though one special chest for a sidequest contains a lore-relevant riddle that requires you to learn the answer before you can open it.
- In Impure Blood, Dara uses it twice:
- In Girl Genius, Violetta inverts it, thinking that Moloch's ability to get into the rafters shows he must have been trained or have some secret knowledge. He assures her that he knows he doesn't want to get munched on by the thing below them.
- In Erstwhile, the prince questions the bride about things during the ceremony and says if she doesn't know them, she's not his true bride.
- In Rusty and Co., the bottle fairy has forgotten her Riddle Me This, and replaces with a riddle that no-one would know.
- In Grrl Power, Sydney puts Leon to the test before verifying that he is indeed a proper nerd.
- In Assigned Male, Stephie asks for a passphrase from Ciel so that she can allow the latter to enter her house, but Ciel doesn't know what it is. Eventually, Steph reveals it to be "Do you want a hug?"
- In Avatar: The Last Airbender, the members of the White Lotus, an Ancient Order of Protectors that works for world peace, use a series of these to identify one another in public, all centered on the checkers-like game of pai sho. The first is placing the white lotus tile in the center of the board on the first move; the second is a Trust Password ("I see you favor the White Lotus Gambit. Not many still cling to the ancient ways." "Those who do can always find a friend."), presumably to weed out those who use the tile by accident; and the third is arranging the tiles in a giant lotus shape, just in case the first two methods fail.
- In the Futurama episode "Fear of of Bot Planet", two characters in disguise must prove they are robots by passing such a test:
Robot #1: Administer the test.
Robot #2: Which of the following would you most prefer? A: a puppy, B: a pretty flower from your sweetie, or C: a large properly formatted data file?
Robot #1: Choose!
[Leela and Fry whisper]
Fry: Uh, is the puppy mechanical in any way?
Robot #2: No! It is the bad kind of puppy.
Leela: Then we'll go with that data file!
Robot #2: Correct.
Robot #1: The flower would also have been acceptable.
- In medieval times, masons needed a way to know whether other masons really knew their stuff, since they traveled a long way on jobs, failures of skill could be disastrous, and it was really hard to check with those who taught them. Their solution was secret rituals — only a skillful mason would be taught them, so knowledge proved his skill. (The true origin of the Freemasons.)
- To anyone who has ever forgotten a code or password to access an account, this trope applies. Painfully. This Cracked article describes how easy it is to infiltrate someone's email and facebook accounts by guessing their security questions if you know enough about them, which is why you should treat the answers to security questions as passwords. For instance, "What was the make of your first car?" should be answered with something like, "Piece of crap Toyota Corolla" instead of just "Toyota".
- Inverted in some cases — someone who knows too much can appear to have researched a topic artificially out of Genre Savvyness, as one German spy in the US discovered when he could complete a line from the third stanza of the US anthem.
- Inverted with the text editor Vi or Vim where, instead of entering, it's almost impossible to exit the program unless you know how. (Then it becomes really simple).
- One (most likely apocryphal) story dating back to the late 19th century involves people entering an office building to apply for a job. They're told to sit in the waiting room for the boss to be ready. After a few minutes of sitting among the noisy din, one person in the group stands up and marches into the office without being told, and everyone else is told to go home. It turns out that hidden among the noise was the sound of a telegraph machine constantly repeating the words "If you understand this, come into the office now"; only a person skilled enough in Morse code to translate the message and focused enough to block out all of the surrounding chatter was worthy of getting the position (which is often stated to be for Western Union or another telecommunications company).