In the Local Tongue

The Lone Ranger, long since retired, makes an unpleasant discovery.

Apparently, "El Dorado" is native for great...big...ROCK!

—Tulio, The Road to El Dorado

A Comedy Trope where something mystical or cool-sounding turns out to be the native language's word or phrase for something completely mundane or outright negative.

A common variant has a character sarcastically say that the subject matter is "native" (or some other language) for something that typically amounts to "piece of shit."

Please note that this about situations where this is played for comedy, not about words actually meaning something significant in a foreign language.

Examples of In the Local Tongue include:

Film

In the third An American Tail movie, The Chief's Daughter of an underground Native American tribe gives Tony (who'd been hitting on her) the nickname "Poolaook", which he is later disappointed to find out means "turkey".
The page quote is from The Road to El Dorado, where, upon finding the end of the map and nothing but a large rock, Tulio surmises that "El Dorado" is a native term for precisely that.
- This line goes from funny to plain silly when you realize that "el dorado" is a term from his native language, the equivalent of an English speaker saying something like "Apparently courthouse is a native word for hole in the road".
The 2002 film version of The Count of Monte Cristo has this exchange:

Luigi: We shall call him... Zatarra.
Edmund: Sounds fearsome.
Luigi: It means "driftwood."

In Don't Be A Menace Dashiki explains that her name is Swahili for "doggy-style."
In 50 First Dates, after Ulla says something deep and meaningful sounding to Henry as they are saying goodbye:

Henry: Thanks buddy, that's beautiful. What's it mean again?
Ulla: Bring me back a t-shirt.

Literature

Used several times in Discworld. For example, the Forest of Skund got its name from a native word meaning "your finger, you fool".
- In Jingo, "Vindaloo" is claimed to translate to "tasteless gristle served to macho foreign idiots."
Discussed in Henry Beam Piper's Little Fuzzy. Some of the names of alien animals and plants are... strange.

You pointed to something and asked a native, and he’d gargle a mouthful of syllables at you, which might only mean, "Whaddaya wanna know for?" and you took it down in phonetic alphabet and the whatzit had a name.

Newspaper Comics

A Far Side cartoon depicts The Lone Ranger discovering that "kemosabe," the "honorific" that Tonto uses when talking to him, means "horse's ass."

Video Games

In World of Warcraft, this is one of the male draenei's jokes:

We did not realize, but in the Naaru language, Exodar means "defective elekk turd."

- Background info: The Exodar is the ship that the draenei took to Azeroth, which crashed on an island. He's implying that the race that created the vessel knew damn well that it was a piece of (pyrotherium) crap.

Web Comics

Inverted in Eight Bit Theater: the character Drizz'l is mocked for his goofy-sounding name, but they shut up when they find out his name means "endless scourge."

Western Animation

In the Phineas and Ferb episode "Run Away Runway", a French fashion designer wants to make Candace a model because her unusually long neck worked perfectly with his new design. He butters her up by calling her his cou de crayon, which Ferb notes at the end of the episode is simply French for "pencil neck."

Urban Legends

An old Urban Legend concerning Spanish conquistadors says that, upon arriving on the Yucatan Peninsula, they asked the natives what the area was called. Due to the obvious language barrier, the natives replied "yucatan," meaning "I don't understand you." Probably apocryphal, but hilarious nonetheless.
- A similar story depicts British explorers in Australia. Noticing large hopping animals, they asked the Aborigines what the animals were called. The natives replied "kan garu" meaning "I don't understand you." Also apocryphal.
- Yet another (apocryphal) telling of meeting natives results in the outsiders realizing that the natives have been giving the same word whenever something new was being pointed at because they were just saying "finger" over and over again.
There's another folk legend about Native Americans and the Spanish. One of the first tribes an expedition came across told them that they would find gold with a mysterious tribe. They were given the name and set off. Every tribe they came to on their journey always said that the tribe they were looking for was just a few days' march away. The name the conquistadors were given was a coded message to the other tribes meaning "These guys are trouble, get rid of them."

Real Life

Jacques Cartier didn't understand the local languages of the Native peoples of what is now Canada as well as he liked his fellows to believe. He misunderstood the designator for what kind of place name he was given, and so gave the country the name Canada (and also led to a city to be named the phonetic variant Kanata). The actual meaning of the word is something like "The Village Of The Small Huts".
Dictionaries of Canadian place names often state that Antigonish (in Nova Scotia) is a Mi'kmaq place name that means something like "The Place Where Bears Get Beech Nuts From The Trees". While Antigonish is indeed of Mi'kmaq origin, and the Mi'kmaq name for the place does translate that way, "Antigonish" actually means something more like "The Place Where Two Rivers Enter The Bay At The Same Place" and isn't a place name at all.
The city of Toronto (in Ontario) is sometimes said to have an Iroquois name meaning "The Meeting Place". It's really a corruption of a word that means "place where trees stand in the water" and was applied to a completely different location on a different lake in a different part of Ontario that was created by a different Native group.