Yes this was a really interesting question and I had to go search:
Bloke: "fellow," 1851, London slang, of unknown origin, perhaps from Celt. ploc "large, stubborn person;" another suggestion is "Gypsy and Hind. loke "a man."
Modern Language Association (MLA): "Bloke." Online Etymology Dictionary. Douglas Harper, Historian. 12 May. 2008. .

Also:
English to American Dictionary:
this is not meant to be authoritive I am sure. :)
bloke n guy. A bloke is a Joe Public, a random punter — any old fellow off the street. Unlike guy, however, it can’t apply to your friends. You can’t walk up to a group of your mates and say “Hi blokes, what’s up?,” as they’d all peer at you as if you’d been reading some ill-informed, cheap dictionary. Without question, the most common usage of the word is in the phrase “some bloke in the pub.”

World Wide Words:
In British slang a bloke is a male person, a term known from the middle of the nineteenth century. Interestingly, it turns up slightly earlier in Australia, where it referred to the boss or the man in charge (also as big bloke). It’s still common in the UK, where it has much of the sense of the American guy (“There was this bloke down the pub ...”) and where to say “He’s a good bloke” is to give high praise. Americans often think of it as British slang, but in the nineteenth century it was common in the USA and is still to be found. However, at one time, Americans also used it in the sense of a stupid person.
For a long time, the experts were unsure where it came from. Some, especially in the United States, suggested it derived from the Celtic word ploc, a large, bull-headed person. Others have suggested that the “stupid person” sense may be from the Dutch blok, a fool, which is where we get blockhead from.
This “stupid person” derivation is probably correct, but we’re now fairly sure that the word in the sense of a man derives either from Romany, the language of the Roma or gypsies, or more probably from Shelta, an ancient secret language used by Irish and Welsh tinkers and Gypsies. It may ultimately derive from Hindi loke, a man.
A slightly earlier word of the same sense, gloak, may come from the same source (in the slang of the early nineteenth century, a buzz-gloak was a pickpocket, where to buzz was to pick a pocket).

There seems to be several legitimate sources for the word and they all seem to have the same meaning.