"Hel he cast into Niflheim, and gave her power over nine worlds, that she should appoint abodes to them that are sent to her, namely, those who die from sickness or old age."
(Terry translation, Poetic Edda)
Whatever appearance the Goddess Hel may have originally taken in ancient Paganism has been lost amongst the letters of Christian hands. Some modern Heathens based on folk ethymology link her to the Godess Holde. But High German Hölle and Helle will never equate High German Holle no matter how you twist the sound shifts. And the subterranean domain of Holda/Holle are as often found under ponds as in mountains (which it might be good to add Thor's followers were said to enter a mountain after death as well). Grimm notes that "Hel, the death-goddess, does not destroy, she recieves the dead man in her house, and will on no account give him up. To kill a man is called sending him to her. Hel neither comes to fetch the souls fallen due to her, nor sends messengers after them." in Teutonic Mythology. This further dispells the idea Hel is Holda, as Holda reguarly lead the Wild Hunt taking the unsuspecting with her.
*Nifolham (Niflheimr) or *Nifolhel (Niflhel) is her home. It seems to be a pleasant place in some areas, in others a dark and forboding place of shades. Beneath it is *Neostrand (Naströnd) the abode of punishment where snakes forever drop venom on the wicked. She is according to the Eddas, a daughter of Loki by Angrboði. She is half black and half of human colour, sometimes described as half living human and half corpse. Outside the Eddas, continental and Anglo-Saxon sources seem to portray her as a greedy, hungry, female deity. A poem in Middle High German ascribes gaping yawning jaws to her as does the Christian Anglo-Saxon poet Cædmon. This view may be why the giantess Thok refused to weep with the added words of "Let Hel keep what she has! "