Do you mean, in other people's campaigns?
There's a well-developed language thingy for Forgotten Realms, mainly because Ed Greenwood is a details freak. Each human region has its own language (and indeed, its own regional feats). There's details about which regions are at war with each other, which are trading with each other, etc. Each race has its own home spot (if not actual home land). There's even specific prestige classes for some regions (Red Wizard of Thay is one). Ed's been working on it for 25 years now…
For our campaign, I'll have a "if your character comes from here you could be/know this" list soonish.