Remus Lupin- Wolf-like.

Nimbus (2000-2001)- In Greek Mythology, Nimbus is a storm cloud that, after reaching the ground, becomes a God or Goddess.

Argus Filch- To "filch" means to steal and Argus is a mythical creature with eyes all over it's head

Rubeus Hagrid- In an interview Rowling said that "Hagird" means hung over, which Hagrid is a lot...

Patronus- Patronus means protector so "expecto patronum" would be expect a protector.

Minerva McGonagall- In Greek Mythology Minerva is the Godess of Wisdom.

Severus Snape- Severus means severe (duh), and Snape is a town that Rowling had once visited.

Albus Dumbledore- Dumbledore means bumblebee, which I suppose would fit...

Draco Malfoy- My favorite secret meaning because it fits so well! Draco means dragon and Malfoy means mistake, so his name would be dragon's mistake!

Sirius Black- Dog Star

Voldemort- the names come from Voldemortist, which means "Lord of Evil". The legend says that Voldemortist tried to destroy Merlin before the time of King Arthur by bribing the evil and bewitching the good. In French Voldmort means "Flight of Death".

Sybil Trelawny- Sybil means "one who can predict the future".

Ludo Bagman- a bagman is a person who collects money for loan sharks all illegal gambling and Ludo means "To Play", fits perfectly :)

Fleur Delacour- "Fleur" means flower and "de la cour" means of the court, so flower of the court.

Olympe Maxime- Olympe is kinda like Mount OLYMPUS and Maxime means maximum, biggest

Crabbe and Goyle- OK, switch the first letters of the name, you would have Grabbe and Coyle, like grab and coil, like what a snake does with it's prey!

Hermes- a messenger for the Gods in Greek Mythology