The Halloween belief goes back a lot further then most people will want to know, since it is before Genesis. It is use at the end of a full moon, when the leaves have fallen from the trees, when the crops are in, before winter sets in. The wearing of animals skins and head dress was to blend in with a herd, for a easy hunt. Deer hunting occurs in the fall when the deer are engage in mating. Deer can be rather mean if they see a rival or enemy (man).
This practice has been used for 10 of eons. It is practice in all cultures across the planet.
When man brought in religion to explain the actions of other cultures did the real meaning lose out. Only man can see spirits in the hot wind on a summer day.