This is precisely the question that brought me to Mudcat ... Some 13 years later?! It seems there's little out there on this fellow, or I trust some Mudcatter would have posted the answer by now.

Oh, well, I can refresh the page, and give a little more context, and maybe that will lead to something more fruitful.

Anyway, I was writing last night in my blog/journal (whatchamacallit) about how the idea of "Geek" is far broader and deeper than an interest in computers, science and comic books. And I turned to Hamlet's soliloquy at the end of Act 2 for my evidence (The speech that ends with: "The play's the thing / wherein I'll catch the conscience of the king!")

But it's toward the beginning of that speech where John-a-dreams is alluded to (first third, or so... the lines in my source were not numbered):

.. .. .. .. Yet I,
A dull and muddy-mettled rascal, peak,
Like John-a-dreams, unpregnant of my cause,
And can say nothing . .. ..

And yes, the name pops out at me every time, ever since I've heard Gordon Bok's cover of the song...

Okay, from these two lines and two line fragments, here's what I can figure out:

"Dull" -- a simpleton? or maybe a Fool figure?
"Muddy-mettled" (mettle -- how something is made, or made of -?) So is he of muddy or unknown substance? A shape-shifter, perhaps?

So he might either be, A) a bringer of dreams, a precursor to the later figure of the Sandman. That's always been my first guess... But he could also be B) a human folk character who was (perhaps) driven mad by a dream... In Midsummer Night's Dream, the rustic clowns talk about the Man in the Moon story, and reveal that he was once human, and sent to the moon as punishment for theft. So it's conceivable that John-a-dreams is something similar.

More questions... Sure would be nice to see some other reference in (some earlier) story or song for more context.