I know some of them. Do you know are these made up or they have a deeper meaning?
Venya, Solania, Mertion, Jovar
Dothion, Shurrock
Belierin, Thalasia
Krigala, Brux, Karasuthra
Ossa/Aquallor, Pelion/Mithardir
Nidavellir
Cathrys, Minethys, Colothys, Porphatys, Agathys
Oinos
Chamada, Mungoth, Krangath, Khalas
Minauros, Maladomini
Avalas, Thuldanin, Tintibulus, Ocanthus
Yeah, those not in the list are from real world mythology or literature like Dante's Inferno.
Oh, so you were only looking for those on the list you'd given? Well, Nidavellir translates to 'dark fields', but I've otherwise covered that one already, as well as my thoughts on Minauros. Maladomini seems to me to stem from Latin (or pseudo-Latin) mala (bad/evil, etc.) and dominus (master). Tintibulus reminds me of the condition tinnitus (the perception of sound within the human ear in the absence of corresponding external sound) which, given the nature of Acheron's continuously drifting and colliding cubes, I imagine is probably the root of that name.
Aquallor simply sounds to me like a made up name for an aquatic region, Solania sounds like it has solar correlations, and you could probably find a translation for Mithardir in Elven language resources.
That's all I've got for the moment.
Thanks, I did find that Mithardir is ''white dust''.
Venya, Solania, Mertion, Jovar is Venus, Sun, Mars, Jupiter (Ptolemy's system of planets).
Mt. Ossa, Thalassia, and mt. Pelion, names from the Greek mythology, different places.
Oinos means "wine" in Greek. I'm not certain why this became a name for one of Hades's layers, but Wikipedia says this:
Or maybe it just comes from the fact that the wine-dark river of the underworld, the Styx, flows through it and helps define it.
The layers of Mount Celestia are named after the planets because in Dante's Paradisio, the spheres of Heaven are named after the Ptolemaic celestial spheres.
Likewise, the layers of Baator are named, for the most part, after features of Dante's Inferno. Malebolge is named for the evil bolges, or pockets, found in the Eighth Circle, while Maladomini is named for the bolgia devoted to evil rulers. Caina comes from the part of the Inferno where Cain is frozen (round one of the Ninth Circle), Nessus is named for the outer ring of the ninth circle, in which Dante and Virgil are escorted by the centaur Nessus. One of the game designers, probably Jeff Grubb, had a map of Dante's Inferno that pointed out Nessus's position in the ninth circle, and he used it as the name of the entire layer. Ed Greenwood originally named the ninth layer of Hell "Cocytus," but that became the name of a frozen layer of Tarterus (Carceri) in the 1st edition Manual of the Planes. Cocytus is the name of the frozen lake in the ninth circle in Dante's book.
"Minethus" is from the Greek "Minytheo," meaning to waste away.
"Avalas" comes from Avalon, a legendary island in British mythology where King Arthur went to sleep until he was needed.
"Tintibulus" comes from tintinnabulation, meaning the tinking of bells.
"Ocanthus" probably comes from acanthus, meaning thorny.
Baator? - not a layer - best I've found is that Greek word for ''deep'' is bathus.
Baator comes from the Baatezu. IIRC Baator is a planescape invention, while baatezu came earlier, in the let's-rename-devils monster manual.
Some say baatezu is composed of a mangled 'Baal' root (the Phoenician god/one of the devil's names) combined with the made up -zu suffix, which supposedly means true devil. Hence most devils have adopted the -zu suffix into their species name. (amnizu, etc.)
This leads to all kinds of new headaches though, because of our demonic friends Pazuzu and the glabrezu.
Baator in turn is then used to signify the home of the baatezu. So it uses the same root word, with another suffix. This could be as simple as that baator is shaped like a (inverted) tor. Or maybe it's more far fetched, and it comes from the french word for gold or something like that...
Is there any??
Brux is to clench or grind one's teeth
This leads to all kinds of new headaches though, because of our demonic friends Pazuzu and the glabrezu.
-zu suffix is Sumerian - maybe the name originates from Druaga
I think baatezu and tanar'ri are just made-up fantasy names that J. Paul LaFountain (the author of the 2nd edition Monstrous Compendium Outer Planes Appendix, though this is possibly a pseudonym) came up with because company policy was that they couldn't say "demon" or "devil" anymore.
The same is true for "aasimon," and "aasimar" is just derived from that. And likewise with gehreleth.
I assumed yugoloth is related to Lovecraft's "yuggoth," but there's not really much similarity other than the name.
Why is Muspelheim in Ysgard? wouldn't the fire giants cause it to drop into the lower planes, or there are unknown inhabitants that keep it
Themetically it fits in Ysgard; but you are right that alignment-wise, it isn't ideal to have it here.
Personally, I placed Sutyr and his fire giants on several of the cubes of Acheron then I placed a major planar conduit from Ysgard to Acheron which manifests in Ysgard as a region of fire.
I then had the Ysgardian Vikings or the the Acheron fire giants launching forays into each other's territories (which is risky as the properties of being brought back to life - which is present on both Ysgard and Acheron - only applies to natives of the respective planes). Each group risks permanent death in order to invade and grab territory (a floating cube from Acheron or a floating isle from Ysgard) and drag it back to their home plane to increase their territory
This way, I keep a fiery realm in Ysgard but allow the giants to live where they fit better
I've always assumed the latter. Muspelheim isn't just a fiery place full of evil giants, it's the fires of Creation itself, the primal creative force that thawed out raw potential and turned it into actuality.
It's a great place for fiery chaotic good and chaotic neutral deities, asuras, fiery variants of bariaurs and fensir, angels of flame, firre eladrins, celestial azers, and explorations of the concept of fire as it relates to individualism, freedom, and creativity. Giants live there too, but they don't define it.
I'd also make Ysgardian fire giants more chaotic neutral than lawful evil. They're foes of the Aesir, but their wrath is justified; the Norse gods killed their forebear and drove them out of the other worlds. They aren't in any way good, but I don't really see why they should be evil either. On the Material Plane, a fire giant's desire to burn the world could be considered evil, but in Muspelheim everything is already on fire, and the feud between the Aesir and the Jotuns is little different from any other long-held rivalry between two different tribes. Surtr could still be evil, but they might have other chieftains with more ambiguous morality.
That means asuras, azers and others have their own name for the layer?
I like the conflict between Ysgard and Acheron. Could Ocanthus have solids made out of obsidian, or it should be only ice?
Since this in non-cannon; I suppose you could do whatever you like.
Personally, I had the Acheron cubes of the fire giants ablaze and composed of fire related material (obsidian, solidified flame, etc.) so that one couldn't exactly tell when the passage from the Ysgard "Muspelheim" to the Acheron "Muspelheim" had occurred (except for maybe a change in tone to those beings sensitive to alignment shifts)
But if you are sticking to strick alignments, I suppose it raises the same issues for the frost giants of Jotumhiem. Should there be a major planar rift from Ysgard to a frozen layer of the Abyss?
Personally, I'm OK with this but a lot of people don't like having too many large connections between non-adjacent planes
Since one of the nine "Norse worlds" is Midgard which corresponds to the Prime, I feel fine breaking up the other eight worlds to different planes (Ysgard, Muspelhiem/Acheron, Jotumhiem/Abyss, Hel/Grey Wastes, etc.) I even placed the Vanir (Norse gods largely tied to fertility that appear to have once been a separate pantheon from the Aesir with Odin, etc) on the plane of Elysium (which I tie to themes of life) and I even have my Norse characters see a giant tree trunk in the center of the Outlands instead of a mountain spire.
But others like to have their pantheons in one central location without intruding on others.
Instead of using Acheron, you could also use the Elemental Plane of Fire for Muspelheim and the Elemental Plane of Ice for the Norse world of Niflheim. Focusing on the elemental power of these worlds instead of the alignments of its inhabitants
I'm also ok with multiple connections between planes, or that the fire giants live in several places. Tough I wonder where did they first appear, and about the primal fires of Creation, is the fire in the Outer planes different from the fire in the Inner planes. It's possible that at the beginning the planes were simpler as in the Norse creation myth, and then split off. Jotunheim seems to have different alignments, I think easiest way is then not be be so strict with alignments.
For me Ysgard tends towards neutrality - it's about survival, where locals believe it's inevitable that the world will someday end in fire and/or ice. It should be filled with elemental conduits and vortices. So in that way it makes sense that Vanaheim and Jotundheim are there. Maybe the inhabitants of Asgard have it easier - and could move to an upper plane - but they haven't forgotten the struggles of life.
Many are likely just made up, but several others are taken from real-world mythology. For example:
Each layer of Ysgard (derivative of Asgard) is taken from several of the 'nine worlds' of Scandinavian myth. Muspelheim (translates to 'fire home') was the realm of the fire giants; Jotunheim ('giants home') was the realm of the frost giants; Nidavellir (also known as Svartalfheim, or 'dark elf home') was an underground realm inhabited by dwarves and the svartalfar (dark elves).
In the Gray Waste, Nifleheim ('fog home' or 'mist home') was the Scandinavian underworld; Pluton refers to the Roman god Pluto (Greek Hades).
Regions of the Greco-Roman Underworld included such names as Tartarus, Elysium, Phlegethon, Avernus, the Rivers Acheron, Cocytus, and Styx.
The first layer of Arborea, Olympus, was obviously named after Mount Olympus.
Limbo and Gehenna are less popular afterlives in judeo-christian myth.
As for Baator... Avernus was already mentioned above. Dis appears derivative of Dispater, which was another name for Hades. Minauros may have been derived from King Minos, one of the judges of the Greek Underworld. Phlegethos appears to be taken from Phlegethon (as above). Stygia seems derived from Styx. Cania used to be called 'Caina' in earlier editions of the setting, so was probably derived from Cain. And Nessus was the name of a centaur in Greek myth who came into conflict with Heracles.