Okay, you have to read back several posts to understand all this, but in summary I am warning everyone that - based on some recent research in the Netherlands - there is an imminent mind-flayer attack from space that will turn the world into Greyhawk. The logic is impeccable and can't be argued with, but you need to read the earlier posts starting here, to follow the steps of this geometry-like proof.
Origins of Furyondy. France. Yep. How do I know? Because English is the common tongue. "Okay," you might ask, "How do you know that English is the common tongue?" Read the f***king Gazeteer! Jeez, what language is it in? Now, since there isn't a geographical place in Greyhawk that looks like England, obviously everyone just drove through the chunnel and spread out through all of Greyhawk while the mind-flayers were making high tea out of the people without cars. Then it sank into the water, probably.
How does this indicate that Furyondy is the remnant of France? Because "Fury" means being pissed off, and how do you think the French are going to feel when they discover that EVEN THOUGH England got completely destroyed, French is STILL not the dominant language and that everyone is STILL speaking English? Yeah, that's right. They'll be furieux. But no one can pronounce "furieux" because they all speak English, so when the French tell everyone that they're "Furieux," everyone thinks, "okay, you're a furieux, so you must be from Furiondy, right?" In the face of this, the French people will characteristically become reduced to a sputteringly wrathful incoherence, and since they don't contradict the English speaker, the English speaker walks away saying, "Furiondy, eh? The food is good, but the waiters are rude."
Which brings us to the fact that the MOST English speaking of all English speaking anything are the halflings. When you live in places called things like "Westfarthing," it's pretty clear where you came from. So, the exodus-via-Chunnel that spreads English across Greyhawk as the common tongue is probably halflings. Why does every Englishman over about five feet tall die in the mind-flayer attack? It's because of hedges. All of England is criss-crossed by little hedges and fences that are no taller than five feet. So the short people can hide behind the hedges, but if you're taller, the mind-flayers can see you. Which is why it's only the short English people who make it to the Chunnel and drive through in their tiny Mr. Bean smart-cars to colonize the new geography of Greyhawk. Eventually all those smart cars decompose, since they are made of recyclable materials, and there's no sign of the halfling invasion. Yep, it's just like rock and roll, another British invasion. Only it's hobbits in small biodegradable cars.
Look people, this is real. Could I make this up?