Won is part of a group of words that originally had a
u but were respelled with
o to increase readability. (Imagine how hard it would be to read
wun in modern cursive, let alone Medieval handwriting.)
One is kind of a fluke. It used to be pronounced like
own, and it still is pronounced that way in most words formed from it, like
alone,
only, and
atone. But sometime in the 1300s the long
o sound split into a diphthong starting with the glide sound
w, and it spread and became standard by the 1700s. The OED says the same thing happened with
oak and
oat, but these remained nonstandard dialectal forms.
Out of curiosity, is there some reason why you keep asking questions here instead of in the
Dear Expert thread? I don't really mind—I'll answer questions wherever—but I thought this thread was more for posting humorous stuff.