Yup. The Bengali region is riverine. Fish is one of their staple foods. The other is rice. So they love fish. Most of them who live overseas just can't do without fish and rice. They make about every vegetable with fish. So they take it everywhere. And that's what contributes to their nickname.
Yeah, it's because they tend to eat a lot of fish(stereotype). You should smell what my next door neighbour cooks(she's Bengali), has a properly strong smell, though I've got no idea what it is.
I work at the fish market in Glasgow and everyone with the same name as one my friends gets their second name put done as fish in my phone book. eg Davie fish
I have never, ever heard this before and I'm of a Bengali background myself LOL! I guess it depends where you live and the kinds of friends you have. However, I guessed as soon as you asked the question that it's because it's one of the staple foods - as has been mentioned.
There used to be a Bangladeshi girl in my secondary school and we all used to call her a 'fishy.' Lol, it was jokes. Thanks for bringing back the memories.