Acromantula - gigantic spider

Probably a combination of "akros" (Greek. "extreme") and "tarantula".

Ashwinder - a snake born from an untended magical fire

Quite simply, "ash" (the residue of fire) and "winder" (as in "sidewinder", a snake that moves sideways). A snake that moves from ash.

Augurey - a rather pathetic-looking bird whose cry was thought to fortell death.

An "augury" is a sign of something coming; an omen.

Basilisk - A giant green serpent, controllable only by Parselmouths.

The mythical king of the serpents. According to legend, there are two species of the creature. The first kind burns everything it approaches, and the second kind can kill every living thing with a mere glance. Both species are so dreadful that their breath wilts vegetation and shatters stones. The only way to kill a basilisk is by holding a mirror in front of its eyes, while avoiding to look directly at it. However, even the basilisk has natural enemies. The weasel is immune to its glance. A more dangerous enemy is the cock for should the basilisk hear it crow, it would die instantly. (Encyclopedia Mythica)

Bowtruckle - a tree-guardian

"Bow" can also be spelled "bough", which is a word for a branch of a tree. "Truckle" means "to be submissive", but that doesn't sound as likely. If you have a better idea, post it on the BBS.

Centaur - stargazing creatures that are half-man, half-horse.

A race of monsters believed to have inhabited the mountain regions of Thessaly and Arcadia. They were represented as human down to the waist, with the lower torso and legs of a horse. The were the followers of the wine god Dionysus and are well known for drunkenness and carrying off helpless young maidens. Picture.

Thanks to Steve Bates on HP4GU for connecting the centaurs to Roonwit, a wise centaur and advisor to King Tirian in the seventh Narnia book, The Last Battle. The centaurs from this series also are stargazers and fortune tellers.

Taken right from myth. The unfortunate wizard mentioned in the entry is none other than Bellerophon.

Strangely enough, "crup" is the word for the rump of a horse. This probably is a nod to their strange forked tail.

"Demi" means "partial". "Guise" means "outward appearance". This creature's name is probably a play on "disguise", which is to conceal one's identity.

It has nothing to do with the creature, but "doxy" is slang for a female lover or a mistress.

Translates to "Never Tickle a Sleeping Dragon" in Latin. The Hogwarts motto. Jo said that she wanted a very solid, practical motto for Hogwarts as opposed to the strict "onwards and upwards" mottoes of the schools she attended.

Straight from mythology and folklore.

I'm not sure about the "dug" bit, but a "bog" is similar to a swamp.

This is a definite stretch. "Erk" is similar to "irk", which means "to irritate". "-ling" is an informal suffix used for young creatures, for example "duckling". Therefore, an erklink is something that irritates young.

The name sounds vaguely like "Elephant". It could be a combination of "serum" and "elephant".

Taken straight from folklore. The original fairies, or faeries, bestowed gifts upon newborn children, such as beauty, wealth and kindness. In the subsequent centuries they continued this original function, but expanded their activities into other types of meddling in human affairs.

While the "crab" bit provokes several questions, the "fire" half is rather obvious.

Right from folklore. Although "ghoul" has now become synonymous with "ghost", the ghouls was originally a demon of the desert from Muslim folklore, is able to assume the shape of an animal. It is an evil spirit that robs graves and feeds on the flesh of the dead or on young children. They inhabit lonely places, especially graveyards. They also lure travelers into the desert, sometimes beguiling those traveles by prostituting themselves, and then devouring them. The Arabic ghoul of the wasteland seems to be a personification of the terror of the desert. (Encyclopedia Mythica)

"Glum" (gloomy) + "bumble" (bumble bee)

Right from folklore. Gnomes are small, misshapen, dwarf-like creatures that dwell in the earth. The name 'gnome' was given to them by the medieval scholar Paracelcus, in an attempt to describe the most important of the earth spirits. Gnomes live under the earth, where they guard treasures. (Encyclopedia Mythica)

Straight from Greek myth. The Griffin was a legendary creature with the head, beak and wings of an eagle, the body of a lion and occasionally the tail of a serpent or scorpion. Its origin lies somewhere in the Middle East where it is found in the paintings and sculptures of the ancient Babylonians, Assyrians and Persians. In Greek mythology, they took gold from the stream Arimaspias and, neighbors of the Hyperboreans, they belonged to Zeus. The later Romans used them for decoration and even in Christian times the Griffin motif often appears. Griffins were frequently used as gargoyles on medieval churches and buildings. In more recent times, the Griffin only appears in literature and heraldry. (Encyclopedia Mythica)

Another pre-JKR beast. The hippocampus was a fabled sea animal from Greek mythology. It was found in classical myth. It resembles a horse with the hind parts of a fish or dolphin. The chariot of Poseidon was drawn by a hippocampus. The name comes from the Greek hippos, horse; and kampos, sea monster. Thanks to Encyclopedia Mythica.

Straight from Greek mythology. A legendary animal, half horse and half griffin. Its father was a griffin and its mother was a filly. It is often found in ancient Greek art and appeared largely in medieval legends.

Straight from folklore. A more popular name for this entity is genie. Historically the imp was thought to be a small demon kept in a bottle or ring. When released or awaken the entity served its master in magical, alchemical, or healing purposes. Supposedly there are both good and bad imps. Magicians evoke them in rituals of ceremonial magic and command them with incantations, words and names of power. During the trails of the witch-hunts in the Middle Ages imps became confused with familiars and both terms were used interchangeably in the trails. Supposedly witches sent imps to do evil deeds against innocence people, in return the witched allowed the imps to suckle their blood through their fingers or protuberances on their bodies. (Encyclopedia Mythica)

According to Brewers "Dictionary of Phrase and Fable", a Jarvey is a hackney-coach driver. Said to be a contraction of Geoffrey; and the reason why this name was selected was because coachmen say to their horses gee-o, and Ge-o’ is a contraction of Geoffrey. Ballantine says, that one Jarvis, a noted hackney-coachman who was hanged, was the original Jarvey. Much thanks to Robert Carnegie for the tip!

From Japanese mythology. Kappas are intelligent water spirits who pull little children into the water and drown them, and attack and fight travelers. They cannot live for long on the land, for they must always keep their heads wet. They have long hair, the body of a tortoise, scaly limbs, and an ape face. The Kappas feed themselves with cucumbers and blood, and use cucumbers to travel on them; these cucumbers fly like dragonflies. (Encyclopedia Mythica)

In Scottish legend, the Kelpie is a treacherous water devil who lurks in lakes and rivers, usually having the shape of a horse and rejoicing in or causing drownings. When a tired traveler stops by a lake to rest or to have a drink, he would see a horse, apparently peacefully grazing. When he mounts the horse, the Kelpie dives into the water, but besides wet clothes, the rider gets away unharmed. (Encyclopedia Mythica, Dictionary.com)

"Knarl" would be pronounced the same as "gnarl", which means "to snarl, growl". This probably has to do with its destructive nature.

From Irish legend. Leprechauns are very small sprites who sometimes live in farmhouses or wine cellars. They are known to aid humans and perform small labors for them. Sometimes they ask humans for supplies and furniture, for which in return they give objects which bring luck and fortune. According to popular belief, a leprechaun possesses a treasure (usually a pot of gold) which a human may obtain if he succeeds in capturing one, which is extremely difficult. Even after capture, a person may not take his eyes off of him for an instant, for then he will vanish. (Encyclopedia Mythica)

Possibly "lethal" (deadly) + "fold". Thus, a creature with lethal folds.

"Mackled" means "blurred". Malaclaw = "Mal" (bad) + "claw". Therefore, a creature whose claws bring bad. I have no idea how "blurred" fits into the picture.

The Manticore is a monstrous creature which inhabits the forests in Asia, especially in Indonesia, Malaysia and India. The manticore, considered to be the most dangerous predator in these regions, has the body of a lion and a head with human resemblance. The mouth is filled with three rows of razor-sharp teeth and the scaled tail ends in a ball with poisonous darts. The monster stalks through the forest in search of humans. Upon an encounter with a human, the manticore fires a volley of darts at the victim, who dies immediately. This unfortunate person is devoured completely, even the bones and clothing, as well as the possessions this person carried, vanish. When a villager has completely disappeared, this is considered proof of the presence of a manticore. (Encyclopedia Mythica)

Mermaids are marine creatures with the head and upper body of a beautiful young maiden and with the lower body of a fish. Mermaids sometimes foretell the future and are often accompanied by seals. According to myth, they lure sailors by singing and with lovely music. They live in a kingdom on the bottom of the sea, and it is here they take their prisoners to. From this story, the fear amongst the sailor grew and they thought that seeing a mermaid would cause bad luck: it could predict death by drowning. The belief in mermaids is not limited to a few countries, but there are tales from all over the world (in India, for instance, there are the Apsara, beautiful water nymphs). However, most of those tales were told by sailors who "saw" them on their long journeys. The idea of mermaids and mermen, the male equivalent, could be based on creatures from Greek and Babylonian mythology: Sirens and Tritons of the Greeks, and the fish gods, who were half human and half fish, from the Babylonians. (Encyclopedia Mythica)

"Moko" is the Polynesian lizard-god. (thanks to Elizabeth Quest)

A nod to traditional "grey" aliens. The patterns they leave in fields are what we muggles call Crop Circles.

Niffler - gold-seeking, fuzzy, black creature

Probably derived from "sniffler", which could indicate that it sniffs out treasure.

The phoenix was a legendary bird thought to live near a well in Arabia. It's song was thought to be so beautiful, that even the sun god would stop to listen. Only one phoenix could exist at a time, and they lived from between 500 to 1500 years. When it thought death was near, it would build a fire and throw itsself into the flames. A new phoenix would be born from the flames, who would embalm the old phoenix in an egg of myrrh and bring it to Heliopolis, the temple of the sun. The phoenix represented the sun, which dies at night and is reborn in the morning. A symbol of immortality and resurrection. From Egyptian, Greek, and Chinese mythology; also mentioned in early Christianity. (Encyclopedia Mythica)

Pixie - tiny, mischievous creatures

In folklore, pixies (or piskies) are little people who believed to live on the downs and moors of Cornwall, England. According to one myth, pixies were originally Druids who resisted Christianity, and the more they resisted the smaller they grew. Yet another myth tells of a race of people who were not good enough for heaven, nor bad enough for hell and were doomed to wander the earth forever.

"Plimpy" is similar to "blimp". The plimpy's spherical shape could have led to this name.

"Puff" (fluffy) + "skein" (a length of thread wound in a loose coil). The "skein" bit probably refers to their long tongues.

"Quinta" (5) + "ped" (foot). Compare with "quadruped", which defines any animal with 4 legs.

Similar in name to the "remora", which are fish of the family Echeneidae, having on the head a sucking disk with which they attach themselves to sharks, whales, sea turtles, or the hulls of ships.

From Scottish folklore. Red Cap is a thoroughly evil creature. He is a short, stocky old man with long gray hair and claws in stead of hands. He lives on the Scottish Border in ancient ruins of castles, especially in those with a bloody history of war and murder. He owes his name to the fact that he wears a red hat, which is colored by the blood of his victims. Red Cap moves with remarkable speed, despite the fact that he wears iron boots. He can overcome even the strongest man, unless the intended victim remembers to quote a few words from the bible. (Encyclopedia Mythica; thanks to Elizabeth Quest for the tip)

I'm not sure of the significance, but re'em is the Hebrew word for "horn".

"Rune" (an incantation of mysterious significance, especially a magic charm) + "spoor" (the track or trail of an animal, especially a wild animal). I don't quite understand the significance, but it's still a pretty neat name.

From folklore. A mythical creature, generally resembling a lizard, believed capable of living in or withstanding fire.