Some of these names actually have meanings. For example "Spielburg" is German for "Game city" (someone said it meant "Game castle," but I know cities that end in "burg," not castles). From what I understand, that's the primary reason they called that city that. That it happened to sound like the name of a famous movie director likely came into play later, when they named the Baron of the city. That is to say, I don't believe they really named it after Steven Spielberg. Knowing the Coles' humor, I believe they meant to name it after the German for "Game city," and when they found out that "Game city" in German is "Spielburg," they found that amusing at worked with that.

"Mordavia" is Latin for "Dark Valley" and Boris tells you that.

"Raseir" is an anagram for Sierra. But I don't know how Shapeir got its name. I would guess the name "Raseir" was thought of first, and then someone just came up with a name that sounded similar to Raseir.

I would guess "Silmaria" is Greek for something, but I don't know what. I would guess "Tarna" is Swahili for something, but I don't know what.

As far as Tarna goes...

There are actually a couple of real locations in Africa that are named Tarna.

"Burg" means "walled town" in German. And yes, those are different from castles, and Germans use a different word to describe castles. ("Schloss," incidentally.)

I don't know in what language "Mordavia" means "Dark Valley," but it's not Latin. The Latin words that most closely resemble the name (according to the Oxford Latin Dictionary) are "mordax" (meaning "biting" or "sharp") and "avia" (meaning "grandmother"). Not an unfitting meaning, given the presence of an elderly vampire lady, but a far cry from "Dark Valley."

Actually, there are a few other Latin words spelled "avia." Another one that might be more appropriate would be "a pathless region; a wasteland."

The continent in which Tarna is located is called Fricana, an anagram of African.

Shapeir is a near-phonetic anagram for Persia.

Shapeir also sounds a little bit like the second half of Gundishapur.

Νο, Silmaria doesn't mean anything in Greek (I am Greek).

There is though a very nice trivia concerning a character with Greek name in QfG5:
Kokeeno Pookameeso in Greek means...Red Shirt!

Ha! That's awesome. I never knew he was a reference to red shirts.

It makes sense if you know that Magnum Opus (and Elsa von Spielburg) were originally intended to be full-blown playable characters in QFG5. It would have made the hero look out of place - he only has his actual name of Devon Aidendale (QFG continuity, not Hero U. I don't like Hero U anyway. Devon Aidendale is a more normal name than things like Falcon and Wren as well.) in the strategy guide! Poor Kokeeno was always fated to die. His first name is Red! (So, does that mean that Erana is weak to Dragon type moves? :P) Hell, the manual spells it half out for you. It tells you that kokeeno means red.

It's also funny to note that despite Elsa's higher stats, Magnum actually is a superior warrior to her in every way aside from her better gear. His AI is (from my experience at least) a little bit better in the arena, and he's the one to win the first Rite, barring player interference. Magical leather bikinis give way more AC than mundane sleeveless shirts.

(now, do Devon Aidendale and Willowsby mean anything important?)

On that note, Devon Aidendale's not actually the Hero's canon name, it was a name used for a strategy guide, pretty much.

Same for Willowsby.