For those who don't know the tale of Stingy Jack the gist of it is that Stingy Jack tricked the devil into not taking his soul, not once, but twice. As a result, when he died he was not welcome in heaven but could not go to hell either. He was caught "between the planes of good and evil". Sounds like an appropriate description of Halloween Town doesn't it? Sounds like Stingy Jack would be revered as legendary among trick or treaters for tricking the devil.

Furthermore, Jack Skelington is referred to as the Pumpkin King, as in King of Jack O Lanterns, well it just so happens Stingy Jack was also none other than Jack O Lantern himself. He was given an ember which he put in a turnip (or Rutabaga) to light his way, and got the nick name Jack of the Lantern.

Halloweentown is a place that is evidently some sort of afterlife, but it certainly isn't heaven and it certainly isn't hell. So perhaps after his death Stingy Jack decided to make the most of his experience and once his skin rotted off leaving him nothing but a perpetually living skeleton, he took on his new name Jack Skellington and founded a town for others caught between heaven and hell, a place with less rules and more fun.

One more piece of evidence is that Stingy Jack was named such for a reason, he didn't like to pay money when he could trick someone into paying for him instead. It was probably borderline thievery a lot of the time. Maybe Jack Skellington never truly grew out of the habit, eventually going as far as to steal an entire Holiday.

Let me know what evidence you have for and against this theory and how you feel about it. Did it miss something? Am I reaching a little too far and grasping a little too hard for some of it? Tell me what you think.

But hey, that's just a theory and I'm shamelessly ripping off a catchphrase, thanx for reading.

Edit: u/endwinglet had this theory before me in reply to a fantheory on youtube. I just didn't notice.