Last September I wrote that I wondered whether the word hell has a similar origin to the German word for a cave, Höhle.
I'm still not sure about that point, but in a book called Word Histories and Mysteries; From Abracadabra to Zeus I read that for the Old English, Hell was a black and fiery place, but for the Old Norse, hell was cold. The Old English meaning came about because the Roman Catholic church was the predominant religious system at the time in England and the Mediterranean view of torment - heat - prevailed there.
The Indo-European root behind the word is kel-, to cover, conceal, so hell once meant the concealed place.
So I guess it could be the same root as for Höhle.