My first campaign map was not only a traced and munged version of Norway's Fjords it also stole place names from Scandinavia. Norway & Sweden town / river names populated the glorious Viking Nation of Alnor (<- that name sucks, no idea where I got it, I was a teenager gimmie a break) and the evil Kingdom of K'jore would sound mighty familiar to any Finns. (Sorry, for making you guys the evil ones.)
I've used Greek and Roman names often because there are easy and plentiful examples of them online. But they carry a lot of baggage and are very familiar to gamers. Currently looking for something stranger, Google Empire to the rescue! Google Search for baby names and name generators. Google Maps provides plenty of place names. Google Translate provides everything else.
english red blue green black white
norwegian rød blå grønn sort hvitt
icelandic rauður grænn blár svartur hvítur
finnish punainen vihreä sininen musta valkoinen
irish bán dearg dubh gorm glas
indonesian merah putih hitam biru hijau
swahili nyekundu nyeusi kijani buluu nyeupe
english The red wizard lives in skull mountain.
norwegian Den røde Veiviseren bor i skallen fjellet.
icelandic Rauði býr álfur í höfuðkúpa fjall.
finnish Red Wizard elää kallo Mountain (Punainen velho elää kallo vuori.)
irish An saol draoi dearg i skull sléibhe.
indonesian Penyihir merah tinggal di gunung tengkorak.
swahili Mchawi nyekundu maisha katika mlima fuvu.
To me Icelandic seems more "viking" than Norwegian but heck if I know how to pronounce those words.
Looking for "elvish". Finnish, Indonesian, and Swahili are candidates but none truly satisfy. I really wanted a Hawaiian for that but could not find a translator. Google doesn't do it and all I found were dictionaries which are painful to use. If I wasn't so lazy I might gather data and write or use a markov chain generator.
For creating place names I make translations of common bits; colors, directions, low, high, stream, forest, crossing, etc. for each language I intend to use. Then create english names e.g. "Dark Wood" and use those lists to translate, "Adhmaddorcha".
I build worlds by playing a "mini-game" of civilization. Something like How to Host a Dungeon. In waves cultures form, rise, and fall (probably due to next culture invading/supplanting them). Starting with the oldest culture, my Celtic analogues using Irish, I sprinkle place names around. In the areas that the next culture becomes dominant they modify or replace the old "Irish" names with their own. In some places both names will be used, perhaps old name returning when new culture fades. In other places the old names will survive to the present. This continues for 3-4 cycles of civilization.
This easily builds up a lot of history and "lived in" feeling for a campaign (as well as plenty of ruins, burial mounds, and lost cities for players to explore). Players will know when they travel to Adhmaddorcha it is ancient and wild. Old texts using old, forgotten place names will provide them a puzzle to figure out.