Black Belt in Origami

A character is being threatened with violence, and tries to tough-talk his way out. Only, he can't legitimately claim to know karate or anything remotely scary, so he threatens the opponent with some random foreign-sounding words as a bluff, hoping the enemy will be too dumb to understand. The most common variant involves origami, but just about any foreign word will do.

In fiction, this actually tends to work at least half the time, with the opponent backing away nervously, or at least hesitating long enough for the Big Damn Heroes to arrive. This can easily be subverted, however, if the opponent actually turns out to know what origami/Hitachi/Pachirisu actually is.

Not to be confused with Paper Master. Compare/Contrast My Hovercraft Is Full of Eels, As Long as It Sounds Foreign, I Know Kung Faux. If the character actually does have a black belt in origami, it's Martial Arts and Crafts.

Examples of Black Belt in Origami include:

Film

The Trope Namer - In the Recess: School's Out movie, TJ yells this at the Mooks dragging him off from his escaping friends.
In Ella Enchanted, Ella encounters Mooks bullying the elf Slannen. After he (semi-unintentionally) orders her to help him, she threatens the Mooks with origami. Unfortunately, one of them actually knows what that is.
In the third Teenage Mutant Ninja Turtles film when the Turtles get sent back to feudal Japan, Donatello greets someone by saying 'Konichi wa Wasabi' which Raph immediately lampshades by confusedly asking 'Hello Mustard?'

Literature

In the Doctor Who Virgin New Adventures novel Transit, the Doctor gets past some Japanese Mooks by using the court dialect of the Japanese royal family. They recognised it, but didn't understand it, which was just as well, since he said "Make way, for I am the official keeper of the Emperor's penguins and his majesty's laundry basket is on fire."

Live Action TV

Used by Billy in Soap against his girlfriend's ex, only substituting Tai Chi for origami. Amazingly enough, it works.
- Probably unbeknownst to Billy, Tai Chi is a legitimate martial art (David Carradine is probably the most famous practitioner)
In an episode of Friends, Ross insists that he knows a martial arts technique called "Unagi".

Recorded and Stand-Up Comedy

Comedian George Smilovici's 1984 routine "I'm Tuff" includes the line "Don't hassle me -- I've got a black belt in macrame", possibly making this the Ur Example.

Western Animation

Patty from Camp Lazlo claims to have a black belt in bok choy.
The origami version appears in the Animated Adaptation series of The Faraway Tree.
In one Dexter's Laboratory episode, Dexter lost the ability to speak anything except the phrase 'Omellette Du Fromage' and used it to ace tests, scare away bullies, seduce women, win gameshows, create world peace, release a solo album among other things. Though his scaring away the bullies is probably the most straightforward use of the trope.
A Scooby Doo episode has Shaggy trying to bluff a Chinese ghost by saying "I know Judo, Chop Suey and Chinese Checkers!"
There was one episode of The Simpsons when Homer was trying to bluff his way into getting a veteran's discount by pretending to have served in Vietnam. He shouted several Asian words (up to and including Margaret Cho) as reference to specific battles he was supposedly involved with.