zek – an inmate of a Soviet labor camp
[Russian, from abbr. for zaklyuchënny prisoner, zaklyuchat to imprison, klyuch key]

Welcome to Penal Colony YaG 14/10, now the home of one of Russia's richest men. …. to think of the nighclubbing billionaire in an abandoned uranium mine with a tin canteen, picking breakfast cabbage from irradiated water with the zeks of Siberia, does give the heart strings a tug.
– Times online, Oct.25, 2005

On occasion, used figuratively:

Now former factory workers buy their shoes, manufactured by tireless Chinese zeks, at Walmart—that is if they have enough money to buy shoes.
– mathaba.net, Jan. 6, 2007

Back in the '60s, when foreign films were the rage, half the reason college kids were willing to put up with subtitles in French movies was that the femmes fatales were so frequently dishabille.
– NPR, September 28, 2007

dishabille or deshabille – 1. the state of being partially dressed (and, by more important implication, partially undressed); 2. the state of being very casually, carelessly dressed

femme fatale – a dangerously seductive woman [Wordcrafter note: the term is not generally considered to be a redundancy.]

Each from French. Where else?

This message has been edited. Last edited by: wordcrafter,

More to the point, the deshabille was a sign she was louche...

bong – a water pipe for smoking marijuana, etc.
[from Thai baung cylindrical wooden tube]

Olympic swim legend Michael Phelps has been banned from competing for three months after being snapped apparently smoking cannabis from a bong.
– The Sun, Feb. 7, 2009

Great to see you back at it, Wordcrafter!

favela – a shantytown or slum, especially in Brazil
[from Brazilian Portuguese]

He had become Santa Marta's advocate, lobbying the state bureaucracy one week, a foreign charity the next, demanding they do something for the people of the favela, for the kids who grew up sidestepping sewage in the alleys or scavenging food from the trash mountains nearby.
– Sam Bourne, The Righteous Men

English has taken in words from many languages. But I know of only one that originated as a word (not a proper noun) in an imaginary language, a language that exists only in fiction!

Challenge: Can anyone supply another?

Maybe that explained why he got along so well with that yahoo in the White House.
– Tom Clancy, The Bear and the Dragon

yahoo – a rude, noisy, or violent person

From the language the Houyhnhnms, the intelligent and civilized horses who are the dominant species in a country in Swift's Gulliver's Travels. “Yahoo” is their term for a subhuman humanoid animal that infests their country. Here is Gulliver’s first venture into the Houyhnhnms’ language:

I could frequently distinguish the word Yahoo, which was repeated by each of them several times: and although it was impossible for me to conjecture what it meant, yet while the two horses were busy in conversation, I endeavourer to practise this word upon my tongue; and as soon as they were silent, I boldly pronounced Yahoo in a loud voice, imitating at the same time, as near as I could, the neighing of a horse; at which they were both visibly surprised; and the gray repeated the same word twice, as if he meant to teach me the right accent; wherein I spoke after him as well as I could, and found myself perceivably to improve every time, though very far from any degree of perfection. Then the bay tried me with a second word, much harder to be pronounced; but reducing it to the English orthography, may be spelt thus, Houyhnhnm.

One such is the verb to grok, from Robert A. Heinlein's novel Stranger in a Strange Land, where it is a Martian word.

I thought of hobbit and orc, but Tolkien derived these words from Old English, so they don't count. Hobbits called themselves kuduk in their language. In Sindarin "orc" is orch and in Black Speech it's uruk, but it's presumably a coincidence that these words are so similar to the English word.