Blimey! is used like a swear word. It's an exclamation of surprise. It's very mild, and I don't think anyone would object to it except as slang, or perhaps as vulgar.
But it conceals horrors, which on its longer form gorblimey are partly revealed.
(Gorblimey (or cor blimey), by the way, is only used, as far as I'm aware, by very old people from the traditionally poor districts of London. Those are the areas where nowadays a high-rise rabbit hutch with shower will set you back half a million pounds. If you're very lucky.)
Anyway, blimey. A nasty word which I've never used since I discovered its derivation.
I mean, no one would, would they?
Word Not To Use Today: blimey. This word is short for God blind me.
The puzzle is why anyone would ever have started saying it in the first place.