Alastor - Greek God who sought revenge on people.

Albus Dumbledore-Dumbledore means Bumblebee. Albus is close to a word in Greek, Albatus, meaning white; white Bumblebee!

Arabella - Ara means alter and bella means wars in Latin

Aragog - "Arachnid" means spider. Gig is a giant. Put them together you get large spider

Argus Filch-To filch means to steal, which is what Filch does, confiscations. Argus in Greek Mythology was a creature with a hundred eyes. 

Arthur - Could represent King Arthur. The legend presents Arthur as a leader in ancient times who defeats the Saxons and other enemies. He thereby unites the people of Britain in peace and harmony.

Bagman - "Bagman" is a person who "bags" money 

Beauxbatons - French for 'beautiful wands'.

Dementor - Dementio means to go mad in Latin

Draco Malfoy- In academic language, Draco means Dragon

Draco Dormiens Nunquam Titillandus - Never tickle A sleeping dragon, and I mean it!. Latin in case you're wondering.

Durmstrang - German phrase meaning storm and stress.

Dursley - A town near J.K. Rowlings's birthplace.

Ernie - Named after one of J.k. Rowlings grandparents.

Figg - Figulus means "potter" and figo means "to attach," maybe that means she's Harry's secret keeper.

Filch - To steal.

Firenze - Italian name for the city of Florence.

Fleur Delacour- In French, stands for "Flower of the Court"

Flitwick - A town in England

Fluffy - Was a real beast in an ancient greek myth. "Cerebrus" the three-headed dog was the guarder of the underworld.

Gilderoy - A highwayman known for being handsome.

Hagrid - Name and tale comes from Greek myth. The ancient Hagrid from the myth was the god of Jewels. This god was said to be the kindest of the gods, but Hades framed him for the death of Piraeus's - the killer of Medusa - son. Hagrid was banished from Olympus but Zues allowed him to stay as the watcher of the animals. Hagrid also means hung-over in (Hagrids usually hung over).

Hedwig - A saint that lived in Germany in the 13th and 14th centuries.

Hermes-Percy's owl is named after the Greek Messenger of the Gods.

Hermione - Bit weird, but broken down it looks like this Her mi one, which could mean her and me (mi) are one.

Lockhart - Town in Australia near Wagga Wagga (reference: "Compose a poem about my defeat of the Wagga Wagga Werewolf"?).

Lucious - Maybe means Lucifer (the devil).

Ludo Bagman- Ludo - (Latin) literally means "I am playing". Bagman - Someone who collects money from criminals who then gives it to the head ring leader. This is how Ludo Bagman got his name, because he was once a Quidditch player, and he always goes round gambling -- loosing and recieving money.

Lupin - Lunar means moon. Lupin means Wolf-like. Canis Lupus is the scientific name for wolf.

Malfoy - "Mal foi" means "bad faith" in French. Malfoy has "mal" in it, meaning evil.

Minerva McGonagall- In Greek Mythology, Minerva McGonagall was the Goddess of Wisdom!

Mirror of Erised - Erised backwards is desire (as in "you'll see what you desire").

Moody - Not in a good mood.

Nagini - 'Naga' is snake in Sanskrit.

Nicholas Flamel - Was a real alchemist, and supposedly DID create the Philosopher's Stone (not "Sorceror's"). The tale was that he had spent decades of his life trying to create the Philosopher's Stone, which could turn any metal in to gold and unlock the secrets to immortality, but could not figure it out.

Nimbus - Nimbus means cloud. Nimbus was also a god in Greek Mythology.

Norris, Mrs. - A Character in one of J.K. Rowling's favorie author's (Jane Austen) books.

Parvati - Parvati is a Hindu Goddess married to Hindu God Siva the Destroyer. She gave birth to a baby boy named Ganesh, who Siva beheaded, but replaced the old head with an elephant head after Parvati reamed him out.

Patronus - Means protector (In Latin I believe).

Peeves - "Peeve" means "little devil" or something that gets on your nerves (like a pet peeve).

Penelope - The wife of Oddyseus and queen of Ithaca. she waited faithfully for her husbands return even though she had many suiters.

Remus Lupin - Remus and Romulus were the founders of Rome. They were abandoned as children and were brought up by wolves. Lupine means 'pertaining to or resembling the wolf.'

Ronan - An irish saint

Ronald Weasley - Ronald Weasley might have come from Running Weasel, a great chess player in history. Running Weasel never lost a game in his life, but he was killed when his rat (Scabbers) knocked over a lamp in his castle, therefore burning it. He was killed

Rubeus - Meaning Rubees. 

Severus Snape- Severus might have come from the word 'severe', being harsh. Snape was a town that J.K. Rowling once visited.
or Sever means cut off obviously. Add that to "us", it could mean Sever Us (as in kill us). Severe also means cruel, grumpy

Sibyll - Sibyll comes from the Sibyls, who were famous propheys in mythology. She was a priestess in ancient Greece who interperted the oracles of the gods of Delphi. As she slept Mother Earth spoke to her and she repeated the magical words the priests. They interperated the meanings and ecplained the prophecies.

Sirius - Named after Sirius Star, or Dog Star. Seen during summer "dog" days.

Stan - Named after one of J.K. Rowling's grandparents.

Tom Marvolo Riddle - If you rearrang the letters it spells: "I am Lord Voldemort."

Voldemort, Lord - There was a dark wizard in mid-evil times named Voldermortist. In another language, Voldermortist means "Lord of Evil" or "Dark Lord".