Excuse me, being English and a frequent user or the word bloody, I'd have to disagree with some points. - Firstly, it's certainly not archaic. Old, maybe, but not archaic as it is still in common usage today. - Secondly, it is most certainly not very vulgar. It's a very light hearted and unoffensive swear word in the scheme of things, as with bugger, git and sod, which are all quite acceptable (although still not polite). I could even get away with saying those words in front of my mother (although I'd probably get a scowl), whereas with some swear words, like crap, sh*t, etc, I'd probably get a shoe thrown at me. It is most likely it have been a corruption of 'by our lady', which was an archaic curse. I doubt it is an actual reference to blood, although I think the if the word 'bloody' hadn't already existed and been in usage I doubt it would have corrupted in the same fashion. Covered in blood is also 'bloody'. In the same way that 'stalk' can mean part of a plant or the action of stalking someone; or 'bill' can mean something you need to pay or a duck's beak.