Place Names:
When a GM tells me that we are in the city of Gragg, capital of the kingdom of Gragg, I know I’m in for a rough time. How many capital cities share their name with a kingdom?
In England, only one county (Durham) even shares its’ name with its’ county town (Durham). But the locals all say ‘County Durham’ or ‘Durham City’ to differentiate between the two. My advice for place names. If you’re creating a land with shires, or counties then make up a suffix name (e.g. tarth) or simply use the English shire, so the town of Sleeford is county town of Sleefordshire (or Sleefordtarth). All you really need for place names, especially in Engish, is a series of suffixes, you can even pinch a history of invasions from place names.
Places were originally named in Old English, Norse, Scots, Welsh, Gaelic or Cornish, according to landscape features (topography), nature of settlement (habitat – city, town, village, fortifications) or the people or tribe living in the area, often combining two or three descriptive terms in one name. These names were then influenced and modified at various historical periods through language shift driven by socio-economic and political changes.
This list of suffixes (and some prefixes) is partly taken from wikipedia, but with some additions of my own. All are accurate for England and the Scottish borders, there are some Welsh ones (the ‘ll’s), but mostly border names.
aber, afon (avon), ash, ast, axe, ay, ey, beck, bex, borough, brough, burgh, (note these three are ALL pronounced boro'), bourn(e), brad, bre, bridge, brook(e), burn, bury, by (viking), canter, carden, caster, cester, chester, caer, castle, cheap, chipping, combe, cot, cott, cotte, dale, deanas, don, dun, exe, fax, field, fin, ford, glen, ham, head, hithe, hythe, hope, houses, hurst, ing, inver, isle, keld, kin, king, kyle, lan, lhan, llan, lake, land, lang, law, low, lea, ley, magna, mere, mon, mouth, nan, nans, nant, ness, nor, parva, pen, peth, pit, pol, pont, port, pyll, shaw, stan, stead, stoke, stone (this was probably once ???'s-ton), strath, street, sud, sut, swin, thorp, thorpe, thwaite (the last three are (IIRC) viking), tre, tilly, toft, tor, tun, ton, water, wick, wicke, worth, worthy, wardine.
Most english towns and cities (and many US/Canadian ones) use these. Lon-DON is in there and so is Wash-ING-TON (a small town in north east England - I believe the Yanks pinched the name

) Sometimes the names are used alone (STOKE) sometimes combined (Bas-ING-STOKE) but you don't need many to create a lot of english sounding place names. I suspect that it's the same for namy other nations.
There are a lot of rivers which share the same name: Avon, Derwent, & Ouse seem particularly popular.