'Nu' is an (extremely) uncommon reading of the kanji 寝 (sleep). Maybe there's a connection, since they always seem to be dozing off.

The weaker type that appears in the Dinomen Hideout and elsewhere.

Short for "marmoset", I think. Possibly related to "mammal", but that seems like a stretch.

The 15th letter of the Greek alphabet, and identical in appearance to the latin 'O'. According to The Chrono Compendium, this is the one that summons some monsters in the Abyssal Temple, then runs away. You can't fight it without modification.

Possibly related to じゃり (jary) = gravel

'Maru' is 丸 = round, but I can't guess what the rest is supposed to mean.

'Waru' is 悪 = bad/evil.

Giga Gaia's left arm (on the right side of the screen), Lavos version. No name.

This resembles ほうおう (houou = phoenix), but is much closer to ホーホー, the noise an owl makes (thanks to Hyena 20 for the latter).

No apparent meaning beyond the obvious similarity to the previous name.

Giga Gaia's right arm (on the left side of the screen), Lavos version. No name.

No apparent meaning. Spelling based on ジャンヌ = Jeanne.

This name is blank in both versions.

カム (kamu) is a verb meaning "bite", but ツインカム also refers to a "twin cam", an internal combustion engine with two camshafts. Credit to Hyena 20 for inspiring me to reinvestigate for puns on this one.

This name is blank in both versions.

Doesn't appear anywhere. Can't fight without modification.

First battle.

Rafflesia is a genus of giant parasitic flower. It's also a fairly common foe in RPGs, and often badly misspelled.

たかねのはな also figurately means something that's visible but unattainable.

Possible pun on "bone man"

At least, that's what it sounds like, even if it doesn't make sense.

Giga Mutant's "foot", has no name.

Tera Mutant's "foot", has no name.

"Melfikk" doesn't seem to mean anything, so I just picked a spelling that looked good.

This name is blank in both versions.

The stronger type that appears in Tyran Castle.

Where do they get these names?

This name is blank in both versions.

A Klein bottle is sort of the three-dimensional equivalent of a Mobius strip. Because of the nature of the shape, it can't actually exist in fewer than four dimensions.

"Beetle" is obvious, but the first part has no apparent meaning. Hyena 20 suggests a pun on "ishito" = "fossil", but fossil in Japanese is 化石 (kaseki) and I can't find any such word as "ishito". It would make some sense, though.

According to The Chrono Compendium, these are the frogs you see in the Underground Waterway Ruins. You can't actually fight them without modification.

This name is blank in both versions.

Likely connection to がっさく (collaboration), especially given the cooperative attack with the winged primates. Thanks to Hyena 20.

No apparent meaning beyond "moss".

The Japanese is spelled a bit oddly, so I spelled the English oddly too.

This name is blank in both versions.

One of the four mythological Chinese gods who govern the four quadrents of the sky, Genbu (玄武 in kanji) appears as a tortoise and rules over water and the northern sky.

See the above entry.

No apparent meaning, other than the similarity to #101.

The fake save points in Magus Castle, no name.

"Sand" makes sense, but there's otherwise no apparent meaning except the similarity to #99.

The "head" of Mini Lavos R, found in the Black Dream. No name.

No apparent meaning.

Without hammer. No apparent meaning.

According to The Chrono Compendium, these are the monsters that fall off the conveyor belt in Vinnegar's Manor. You can't actually fight them without modification.

With hammer. No apparent meaning.

This name is blank in both versions.

This name is blank in both versions.

No apparent meaning. デッカ could be from でかい = huge.

This is the one found in the Guardia Castle dungeon.

No name. This is an alternate Nu that has no rewards for winning, nothing to steal, and less magic power than usual. I'm not sure where it's used, if at all. Possibly an NPC somewhere.

No apparent meaning.

No apparent meaning.

Appears only as an NPC. You can't fight him without modification.

Thanks to Mew seeker for noticing that the pronunciation matches the French word scarabée, meaning "scarab".

Name is derived from デブ (debu), a rude term for the overweight. Thanks to Hyena 20.

No apparent meaning.

No apparent meaning.

No apparent meaning.

Magus Castle version, without sword.

Magus Castle version, with sword.

Magus Castle version.

Three-on-three battle.

Short for "mutant", of course.

Three-on-three battle.

Probably the version on Zenan Bridge.

Magus Castle version.

No apparent meaning.

"Saurus" is obvious, the rest has no apparent meaning.

No apparent meaning.

Battles Cyrus in Frog's flashback, and doesn't appear elsewhere.

Appears only in the programmers ending. Can't fight without modification. "Bouzu" (Buddhist priest) can also be used like "kid".

The head in the second battle.

Zeal's right hand (on the left side of the screen), no name.

Zeal's left hand (on the right side of the screen), no name.

The bottom half.

Junkdragar's top half, no name.

Melfikk's bottom half, no name.

Melfikk's top half, no name.

Mega Mutant's "foot", no name.

Single battle.

Single battle.

This name is blank in both versions.

Could also be the name Daigoroh.

Imitating Guard Machine.

Imitating Hekeran.

Imitating Junkdragar (top half).

Imitating Gran and Leon.

Imitating Nizbel.

Imitating Magus.

Imitating Dragon Tank.

Lavos interior, torso. No name.

Lavos interior, right arm (on the left side of the screen). No name.

Interior, left arm (on the right side of the screen).

Center part.

Giga Gaia's left arm (on the right side of the screen), no name.

Giga Gaia's right arm (on the left side of the screen), no name.

The "head" of the above Mini Lavos, fought on Death Mountain. No name.

Dragon Tank head, Lavos version. No name.

Dragon Tank wheel, Lavos version. No name.

Bit, Lavos version. No name.

This name is blank in both versions.

Junkdragar bottom half, Lavos version. No name.

Azarla, Lavos version. No name.

Spekkio changes forms as your levels increase. His forms are listed from weakest to strongest.

Imitating Black Tyranno.

Imitating Giga Gaia.

Abyssal Temple version, the one you're supposed to lose to.

Normal version of the shell.

Lavos core bit, screen left. No name.

Pun on escargot?

Lavos core bit, screen right. No name.

This name is blank in both versions.

Appears only as an NPC. You can't fight him without modification.

Son of Sun's flames, no name.

Magus Castle version.

Northern Cape version.