Before we go over what the names mean, let's cover a few important things. Dragon Quest 9 only recognises maps by two specific things: Quality and a random seed. Quality is a number between 2 and 248 that determines how good a map might be, and the random seed gives one of 32768 maps of that quality. So that means there are over 8 million maps in the entire game. So far, so good.

The quality of a new map is based on the hero's level and the level of the grotto you just completed. The basic formula is in fact as follows:

New Quality = Hero's Maximum Vocation Level + 5 * Hero's Maximum Revocation + Level of Previous Grotto

Only the hero's levels count (the rest of your party doesn't), and only your maximum levels/revocation count. So if you're currently an L1 Luminary, but you have L50 in Minstrel, then you count as an L50 character. And if you've used revocation on your Warrior class twice, but your Gladiator class three times, then you count as having used revocation only three times for the purposes of grottos. Note that you can only use revocation on a single class a maximum of 10 times.

And no, getting yourself killed will not increase the quality. It's revocation only.

This quality can also vary by up to 10% in either direction, so a base quality of 100 could actually be anywhere between 90 and 110. And as stated previously, Quality is capped at 2 minimum to 248 maximum.

Once we have a Quality for the map, the three primary stats of the map can be generated via the random seed. These are how deep the map is, how strong the monsters on the first floor are, and what boss lurks at the bottom. They are randomly determined based on the quality:

Quality 2 - 55 2-4 Floors Rank 1-3 Monsters Boss #1-#3 (Equinox, Nemean, Shogum)
Quality 56 - 60 4-6 Floors Rank 2-4 Monsters Boss #1-#3 (Equinox, Nemean, Shogum)
Quality 61 - 75 4-6 Floors Rank 2-4 Monsters Boss #2-#5 (Nemean, Shogum, Trauminator, Elusid)
Quality 76 - 80 6-10 Floors Rank 3-5 Monsters Boss #2-#5 (Nemean, Shogum, Trauminator, Elusid)
Quality 81 - 100 6-10 Floors Rank 3-5 Monsters Boss #3-#7 (Shogum, Trauminator, Elusid, Sir Sanguinus, Atlas)
Quality 101 - 120 8-12 Floors Rank 4-6 Monsters Boss #4-#7 (Trauminator, Elusid, Sir Sanguinus, Atlas)
Quality 121 - 140 10-14 Floors Rank 4-6 Monsters Boss #5-#9 (Elusid, Sir Sanguinus, Atlas, Hammibal, Fowleye)
Quality 141 - 160 10-16 Floors Rank 5-7 Monsters Boss #6-#9 (Sir Sanguinus, Atlas, Hammibal, Fowleye)
Quality 161 - 180 10-16 Floors Rank 5-7 Monsters Boss #7-#10 (Atlas, Hammibal, Fowleye, Excalipurr)
Quality 181 - 200 11-16 Floors Rank 6-9 Monsters Boss #8-#12 (Hammibal, Fowleye, Excalipurr, Tyrannosaurus Wrecks, Greygnarl)
Quality 201 - 220 12-16 Floors Rank 8-9 Monsters Boss #1-#12 (Equinox, Nemean, Shogum, Trauminator, Elusid, Sir Sanguinus, Atlas, Hammibal, Fowleye, Excalipurr, Tyrannosaurus Wrecks, Greygnarl)
Quality 221 - 248 14-16 Floors Rank 9 Monsters Boss #1-#12 (Equinox, Nemean, Shogum, Trauminator, Elusid, Sir Sanguinus, Atlas, Hammibal, Fowleye, Excalipurr, Tyrannosaurus Wrecks, Greygnarl)

Note that the listed number of floors does not include the boss floor, and that for every 4 floors you descend, the Monster Rank increases by 1. So in order to face Rank 12 Monsters, you need a Grotto that starts at Rank 9 monsters and is at least 13 floors deep.

Also, you won't get better maps unless you cross over into the next quality bracket, so you don't need to feel you have to push yourself through the absolute highest level map you have if a slightly easier one would reach into the same bracket.

The game gives you four bits of information about a map to help you figure out what it's like before you enter. These are its Level, Prefix Name, Suffix Name and Environment Name.

Level: A map with 2 Floors (not including boss floor), Rank 1 Monsters on 1F and Boss #1 (Equinox) has a base level of 0. For every extra Floor, increased Monster Rank or increased Boss Rank, an extra 3 levels is added. Finally, a random number from -5 to 5 is added to the level. This means that a map with 10 Floors, Rank 4 Monsters and Boss #7 (Atlas) would be Level 46 to 56.

Prefix: The prefix gives an indication of how strong the regular monsters in the grotto are. This is randomly assigned, so each prefix could be a number of different monster ranks. This is also used to help determine what will be in the treasure chests you find, so it can be pretty important. The prefixes are as follows:

ClayMonster Rank 1-2
RockMonster Rank 1-2
GraniteMonster Rank 1-2
BasaltMonster Rank 1-4
GraphiteMonster Rank 1-4
IronMonster Rank 3-4
CopperMonster Rank 3-8
BronzeMonster Rank 3-8
SteelMonster Rank 5-8
SilverMonster Rank 5-8
GoldMonster Rank 5-8
PlatinumMonster Rank 5-9
RubyMonster Rank 7-9
EmeraldMonster Rank 7-9
SapphireMonster Rank 7-9
DiamondMonster Rank 7-9

Suffix: The suffix gives an indication of which boss awaits you at the bottom. However, since each adjective can cover a number of different bosses, it can only be used as a very rough guide: it's easier to just use the Quality data to determine what boss you should be getting. The suffixes are as follows:

Joy, Bliss, GleeBosses #1-#3 (Equinox, Nemean, Shogum)
Doubt, Woe, DolourBosses #1-#6 (Equinox, Nemean, Shogum, Trauminator, Elusid, Sir Sanguinus)
Regret, Bane, FearBosses #4-#9 (Trauminator, Elusid, Sir Sanguinus, Atlas, Hammibal, Fowleye)
Dread, Hurt, GloomBosses #7-#12 (Atlas, Hammibal, Fowleye, Excalipurr, Tyrannosaurus Wrecks, Greygnarl)
Doom, Evil, Ruin, DeathBosses #10-#12 (Excalipurr, Tyrannosaurus Wrecks, Greygnarl)

Environment: The final piece of information is the actual place name. This has two pieces of information to be gleaned: how deep the grotto is, and what type of landscape you'll find inside the grotto. There are 5 different environs: Caves, Ruins, Ice, Water and Fire. Each environ have their own monsters. The environ names are split into 8 ranks, which are as follows:

Rank 1 Environs (2-7 Floors) Tunnel (ruins), Cave (everything else)
Rank 2 Environs (2-11 Floors) Crevasse (ice), Marshe (water), Mine (everything else)
Rank 3 Environs (4-13 Floors) Icepit (ice), Lake (water), Crater (fire), Lair (everything else)
Rank 4 Environs (6-15 Floors) Snowhall (ice), Moor (water), Dungeon (fire), Path (everything else)
Rank 5 Environs (8-15 Floors) Crypt (all environs)
Rank 6 Environs (10-16 Floors) Ruins (ruins), Tundra (ice), Waterway (water), Nest (everything else)
Rank 7 Environs (12-16 Floors) World (all environs)
Rank 8 Environs (14-16 Floors) Abyss (cave), Maze (ruins), Glacier (ice), Chasm (water), Void (fire)

From all this, you should be able to get a decent working idea of what the maps you're collecting are just from their name, and thus better decide which are worth investigating further.