This is a necessarily long answer, the short answer is the common notion of hell in mediaval times is as simple and as graphic as the common notion of heaven, the universe, and most scientific theory. Remember the sky was a dome, pierced with holes, and it was possible to reach the edge of the world, and alchemists could turn base metal into gold ...
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The English term 'hell' is from the Anglo-Saxon verb 'helan' or 'behelain' - to hide.
Before going into the Hebrew/Greek/Latin, it might be worth considering this: In the Garden of Eden, the result of the eating of the forbidden fruit was that the Primordial Couple saw their nakedness, were ashamed, and hid from the Divine Presence. If we review this process then 'nakedness' implies difference - they saw that they were different from each other - and 'difference' as a concept is dependent upon 'duality'. Prior to this moment there was only Primordial Unity which is without difference or distinction.
Scripture states 'their eyes were opened' - yet it is obvious they were not blind before - so when their (outer) eyes were opened their (inner) eye was closed, or more precisely occluded. In another sense, they saw only the surface and lost the sense of the interiority of things, both as things and as part of a whole - they saw their difference but not why. This sense of loss of understanding, this sudden bewilderment and confusion, is the cause of their shame.
And, shame being found to be lesser than one knows one is, or ought to be, they hid.
Here lies a foundational notion of hell.
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The Latin 'infernus' (inferum, inferi), the Greek 'Hades', and the Hebrew 'sheol' correspond to the word hell. Infernus is derived from the root in; hence it designates hell as a place within and below the earth. Hades, formed from the root fid, to see, and a privative, denotes an invisible, hidden, and dark place; thus it is similar to the term hell. The derivation of sheol is doubtful. It is generally supposed to come from the Hebrew root meaning, "to be sunk in, to be hollow"; accordingly it denotes a cave or a place under the earth.
In all three then, 'hell' is perceived as a netherworld, a lesser world, denied the light of day and thus a place of privation, light in this sense being both material - light, warmth, comfort, etc, and spiritual. If there is suffering in this world, then it is obvious that the suffering of man in the netherword is increased proportionally.
In the New Testament the term Gehenna is used more frequently in preference to hades, as a name for the place of punishment of the damned. Gehenna is the Hebrew g?-hinnom "valley of the sons of Hinnom". The Valley of Hinnom is south of Jerusalem and is now called Wadi er-rababi. It was notorious as the scene, in earlier days, of the worship of Moloch and the sacrifice of children. For this reason it was defiled by Josias (IV Kings, xxiii, 10), cursed by Jeremias (Jer., vii, 31-33), and held in abomination by the Jews, who, accordingly, used the name of this valley to designate the abode of the damned (Targ. Jon., Gen., iii, 24; Henoch, c. xxvi). And Christ adopted this usage of the term as a figurative term to clothe a metaphysical concept.
Besides Hades and Gehenna in the NT there is "lower hell" (II Peter, ii, 4), "abyss" (Luke, viii, 31 and elsewhere), "place of torments" (Luke, xvi, 28), "pool of fire" (Apoc., xix, 20 and elsewhere), "furnace of fire" (Matt., xiii, 42, 50), "unquenchable fire" (Matt., iii, 12, and elsewhere), "everlasting fire" (Matt., xviii, 8; xxv, 41; Jude, 7), "exterior darkness" (Matt., vii, 12; xxii, 13; xxv, 30), "mist" or "storm of darkness" (II Peter, ii, 17; Jude, 13). The state of the damned is called "destruction" (apoleia, Phil., iii, 19, and elsewhere), "perdition" (olethros, I Tim., vi, 9), "eternal destruction" (olethros aionios, II Thess., i, 9), "corruption" (phthora, Gal., vi, 8), "death" (Rom., vi, 21), "second death" (Apoc., ii, 11 and elsewhere).
In all the above references, and their differences, one can see metaphysical symbolism at play.
Might I also add that in the traditions of the east, even non-theist Buddhism, there is sin and hell, and the symbolism of both corresponds often exactly with those of the west, which signifies its universality. An occupant of Dante's Inferno, for example, would find himself entirely at home in a Buddhist hell.
Thomas