Christopher Moore has written a book, In Other Words, about untranslatables (via translation eXchange).
The NPR site lists some of these words/phrases from various languages. It also has an audio link for an interview.
They include ilunga, from the Tshiluba language, which has been done to death in the media.
For German, the word Korinthenkacker is given:
bq. korinthenkacker [core-in-ten-cuck-er] (noun)
A “raisin pooper” — that is, someone so taken up with life’s trivial detail that they spend all day crapping raisins. You can spot these types a mile off — it’s that irritating pen pusher or filing fanatic whose favorite job is tidying up the stationery cupboard.
I don’t think anyone’s ever told Christopher Moore the difference between raisins and currants.
It sounds like a bit of light reading, just listing such a miscellaneous collection. And is this word not chosen because it is amusing, especially to those who haven’t heard it before? It doesn’t seem untranslatable, although the best equivalents are even more colloquial (I suggest a fart in a colander). Collins has fusspot.
Strangely, Lions Club International has the web address www.korinthenkacker.de. And the book Variantenwörterbuch des Deutschen I’ve already lusted after it, but I have too much else to read) gives the synonym Tüpflischeisser.