1.) In Native North American
mythology, the afterlife
. The Happy Hunting Ground is populated not only with one's wise ancestors (ancestor worship
being a strong aspect of Native American spiritual tradition), but also all the spirits of animals properly hunted, with whom the hunter has made peace. There's The Great Spirit
somewhere in there, too.
2.) In the AD&D game universe, the Outer Plane associated with Chaotic-ish Neutral Good alignment. The Happy Hunting Ground of the DDG never sat right with me, and in retrospect, it's because there was no convincing AD&D representation of American Indian shamanism.