Remember how excited you felt when Flocke announced that, unlike Locke, he wants to go home? If you're like me, you immediately jumped at any excuse to call the Island "Atlantis" and to posit that the Egyptian hieroglyphics are present because of the Island's one-time proximity (physical, cultural) to the Egyptian Empire. Smokey's from Egypt!
However! Considering how fast the Others put up all their defenses at the temple when they hear that Jacob's dead, I'm guessing Old Smokey calls the temple "home." Where did he come from? When did the temple originally pop him out? Guys! I have a guess!
1. Smokey can't cross any ring made of volcanic ash. He can knock people out of the ash circumference, like Winifred from Hocus Pocus during her smarter moments, but he most definitely has an undeniable and probably ancient connection to that ash law. Aha, he has to follow at least one law, and aha, those are probably the laws that prevent him from killing Jacob without a loophole.
2. Smokey is made entirely of thick, dark smoke. Smoke that reminds me of a volcano. And I think there are some hieroglyphics underneath the temple that back up the idea that he's heavily connected to a volcano.
3. There was definitely a volcano on the Island - Horace's first wife/schoolteacher taught us that right before the Hostile alarm sounded in Ben's class that one time.
ERGO! I think the Smoke monster was born out of the Island's volcano, and that's why he has to honor the ash circle.
Now you might be thinking, 'Becky, that's not much of a theory at all.' But guess what? I'm trying to figure out HOW to make a theory about Smokey. Now that I've guessed that he's possibly from a volcano, I can ask theoretical questions like:
a. What makes smoke turn into a person? Did the smoke come to inhabit a person, and that was the very beginning of Smokey?
b. Does Jacob come from the volcano, too?
c. What's going on with the volcano in the first place? Some islands are formed out of undersea volcano magma. I believe they're called archipelagos. Nope, I'm wrong. They're called High Islands. An island with crazy streams of electromagnetic energy might have formed because of a volcanic blast caused by electromagnetism. Maybe the Island has a direct pathway to something inside the earth.
Anyways, that's what I have for now. Please! Elaborate!