It is a societal/legal construct brough up from the historical experience (eg. if a caveman built himself a hammer, they possessed it as long as they took good care of it).
We've redefined what "taking good care of something" means for things you possess, and we made elaborate social/legal constructs to clearly define boundaries of possession.
But this is present even in the animal world, even when it comes to "property" (wolfs mark their territory, so do lions, bees go back to their own hives, etc).
>Possession is a physical/real property of the universe
This assertion immediately falls apart on consideration IMO. Even in simple, controlled circumstances like football, the meaning of "possession" is subject to mutual agreement (i.e. "rules").
You could take some particular definition of "possession" as "natural" or otherwise axiomatic. This is not unheard of, but I think it's a trick of misdirection to place it in the domain of the "physical/real" when it is plainly a political matter.
It’s not like you can take anything with you when you’re dead, owning materials is really just a societal construct no matter which way you slice it.