[KyleGoetz]

I've recently come across the term べらんめえ. I understand it's the style of speech that makes ひ into し and あい and いい into ええ. For example, 人は汚い might be pronounced しとがきたねえ. I've know about this speech style for a long time (actually probably for 10 or more years!), but I never had a name for it.

1. Where does the term べらんめえ come from?
2. Are there good resources to read up on it?
3. Are there more "rules" than what I mentioned above?
4. I saw someone refer to 東北 when discussing it; is it related to the dialect there originally? I would have guessed it's an 江戸 thing.

I know young people talk sort of like this sometimes to be "cool," and I kept wondering about the pronunciation of ひ for a couple years because I think one of my professors may have switched into べらんめえ when speaking quickly, thus leaving me confused for a long time (kind of like whether I should pronounce the す at the end of polite forms like です and します...this was another problem for me in college because two of my TAs spoke this way and two did not).

Thanks!