Charley, that's probably because it DOESN'T have any origin in chess...

That Urban Dictionary entry is plain wrong. The original phrase when beating someone by a substantial amount was that you "owned" them, and that phrase originated well before internet gaming. The word "pwn" or "pwned" then came from a simple spelling mistake from ("p" and "o" are adjacent on the keyboard), and gained popularity online until people recently started using it in spoken English. It may be pronounced the same as "pawn", but it is a distinct word in its own right, in the same way that "through" and "threw" are distinct words in their own right - and since it originated in a text-based form, even the pronunciation is not fixed. But two things are clear: it should not be spelled "pawn" (because this is a typo of a typo!); and it does not have (and never did have) any connection to the word or concept "pawn".

Graham.