I think the names are mostly designed to take influence from their real-life counterparts. Some succeed while others fail.
The Swadians, based on English and Teutonic knights, have according names. "Vyincourd" is my favorite example. The Nords, while having some cool names, don't really seem consistent. "Sargoth" might have been spelt "Sargoð" in their mother language (Old English? Norse?) although I can't say it really seems to fit. We also know, by examples like Vayejeg, that their phonetics are much different than historical people's. (The J would traditionally have been pronounced as a Y, but the third letter makes that redundant.) The Khergits probably have the most appropriate naming system, though I'd wager there's some occasional Greek influence there.