Wonk: indicates someone who’s too expert in something. Like a boffin, but (usually) for something at least theoretically useful. People who take part in political-union-style debating parties and debate all the minutiae of national politics are wonks; people who take part in Doctor Who conventions and debate all the minutiae of Dalek vs. Cyberman politics are boffins.

I have never heard either of these terms, although I'm familiar with the species they describe. Which is fascinating. Are they regional?