• Alastor - Greek God who sought revenge on people.
• Albus - In Latin means 'white' or 'wisdom'.
• Arabella - 'Ara' means 'alter' and 'bella' means 'war'. 'War-alterer'?
• Aragog - 'Arachnid' means spider.
• Argus - In Greek mythology, Argus was a monster that had 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.
• Beauxbatons - French for 'beautiful wands'.
• Draco - Draco is a constellation that looks like a dragon but is a snake. In Latin, Draco means 'dragon'.
• Dumbledore - Means 'Bumblebee' in Old English.
• Durmstrang - 'Sturm und drang' is German phrase meaning storm and stress.
• Dursley - A town near J.K. Rowling's birthplace.
• Figg, Mrs. Arabella - 'Fig' means 'not literal'.
• Filch - To 'steal'.
• Firenze - Italian name for the city of Florence.
• Flitwick - A town in England.
• Fleur Delacour - Means 'Flower of the Court' in French.
• Fluffy - 'Cerberus' the three-headed dog was the guardian of the underworld in Greek mythology.
• Gilderoy - A highwayman known for being handsome. May also come from the word 'gilded', which is defined as having a pleasing, showy appearance, which covers something of little worth.
• Granger, Hermione - 'Hermione' means 'messenger'. 'Granger' means 'farmer'. There are also reports that 'Hermione Granger' means 'Earth Farmer'.
• Hedwig - A saint that lived in Germany in the 13th and 14th centuries.
• Hermes - A messenger in Greek mythology.
• Lockhart - Town in Australia near Wagga Wagga ('Compose a poem about my defeat of the Wagga Wagga Werewolf'?).
• Lucius - Similar to Lucifer (the devil).
• Lupin, Remus - Lupus is the latin word for 'wolf'. 'Lupin' means wolf-like. Canis Lupus is the scientific name for wolf. In ancient Roman mythology, Remus was the brother of Romulus (founder of Rome). They were raised by a female wolf. Remus was killed by his brother as they argued over the name of the city. 'Remus' is latin for 'fast-moving'.
• Malfoy - 'Mal foi' means 'bad faith' in French. Malfoy has 'mal' in it, meaning evil.
• Minerva - In Roman Mythology was the Goddess of Wisdom. In Greek Mythology she was the Goddess of War. She gave strict punishments.
• Mirror of Erised - Erised backwards is desire. The inscription around the top of the Mirror of Erised, if shown backwards with the spaces rearranged, says: 'I show not your face but your hearts desire'.
• Moody - Not in a good mood.
• Nagini - 'Naga' means snake in Sanskrit.
• Nicholas Flamel - Was a real alchemist, and he supposedly did create the Philosopher's Stone. 
• Nimbus - 'Nimbus' means 'cloud'. Nimbus was also a god in Greek Mythology.
• Norris, Mrs. - A character in one of J.K. Rowling's favorite author's (Jane Austen) books.
• Parvati - Parvati is a Hindu Goddess (who had a sister called Padma) who married the 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. 'Patel' is a common Indian last-name.
• Peeves - 'Peeve' means 'little devil' or something that gets on your nerves.
• Ronan - An Irish saint.
• Severus - Sever means 'to cut off'. Severe also means cruel, strict. In ancient history, Lucius Septimius Severus restored stability to the Roman empire after the tumultuous reign of the emperor Commodus and the civil wars that erupted in the wake of Commodus' murder.
• Sibyll - Sibyll comes from the Sibyls, who were famous prophets in ancient mythology.
• Sirius - Named after the star Sirius, also known as the Dog Star, and is he brightest star in the sky. It is situated in the constellation Canis Major (latin for 'greater dog'). Sirius' name means Dog Black, or if you flip it around, Black Dog.
• Skeeter, Rita - 'Skeeter' is short for 'mosquito'. As most people can attest, mosquitoes are among the most annoying life-forms on this planet.
• Snape - A town in England, also based after a person JKR knew.
• Tom Marvolo Riddle - If you rearrange the letters it spells: 'I am Lord Voldemort'.
• Umbridge - may be derived from the English word, Umbrage: offence given or taken; resentful displeasure. 
• Voldemort, Lord - There was a dark wizard in medieval times named Voldermortist. In another language, Voldermortist means 'Lord of Evil' or 'Dark Lord'. Legend has it that Voldermortist once tried to destroy Merlin before the time of King Arthur (Mr. Weasley?), by bewitching good people, and simply bribing those who already were evil. Legend has it that Merlin destroyed Voldermortist by using a simple paralyzing charm (full body bind?), fed him to the many-headed-beast (Fluffy?) of the lake, the Lady of the Lake's pet (Giant Squid?), freed the bewitched people, and destroyed the evil men. That was maybe twelve, thirteen years before Arthur (how long it was from Voldemort's destruction until Harry started Hogwarts). In French means 'thief of death'.
• Wealsey, Ronald - Supposedly, in the time of King Arthur, there was a soldier called 'Running Weasel'. This soldier's life was ended by a rat (!) knocking over a lantern and burning him up. The rat had been dyed yellow by other soldiers (just like Ron tried to turn Scabbers yellow) who were looking for a joke. 'Ronald' is the Scottish form of 'Reginald' (Old English) and it means 'powerful and mighty'.

Spells

• Accio (summoning charm) - Latin for 'to summon'.
• Avada Kedavra (killing curse) - Aramaic phrase that means 'may it be destroyed'.
• Avis (spell that Ollivander used to make birds fly out of Krum's wand) - Latin for 'bird'.
• Cunjunctivitus Curse (spell that Krum used to 'do something' to the eyes of the Chinese Fireball during the first task) - Conjunctivitis is the scientific name for pink-eye - the illness that children often get that makes eyelids crust together.
• Cruciatus Curse - 'Crucio' is Latin for 'to torture'.
• Deletrius (banishing spell) - Latin for 'to erase'.
• Densuageo (spell that Malfoy used to make Hermione's front teeth grow huge) - 'Dens' is Latin for 'teeth'. 'Augeo' is Latin for 'to enlarge'.
• Diffindo (spell Harry used to cause Cedric's bag to split apart) - In Latin, 'Diffundo' means 'scatter'.
• Ennervate (used to revive someone who has been stunned) - When spelled with two n's, as ennervate, it actually means to add nerve (daring or strength). 
• Expecto Partonum (patronus charm) 'Expecto' means 'expect' and 'patronus' means 'protection'.
• Expelliarmus (disarming spell) - Latin combination 'to expel' and 'arma' (weapon).
• Impedimenta (used to slow down attackers) - 'Impedio' is Latin for 'to hinder'.
• Imperius Curse - 'Impero' is Latin for 'to control' and 'imperium' is Latin for 'absolute control'.
• Lumos (used to make a wand emit light) - 'Lumen' is Latin for 'light' and 'luminous' means 'emitting light' in English.
• Morsmordre (makes the Dark Mark appear in the sky) - Combination between 'mors' (Latin for 'death') and 'modere' (Latin for 'to bite'). Death bite? No - Death Eater.
• Nox (cancels out Lumos) - 'Nox' is Latin for 'darkness'.
• Orchideous (makes flowers spring out of the tip of a wand) - Orchid is a type of flower.
• Quietus (cancels out 'Sonorus') - Obviously 'quiet' means to be silent, and 'quietus' in Latin means to be quiet.
• Reducio (shrinking charm) - 'Reduce' means 'to make smaller' in English.
• Riddikulus (spell used to transform a scary Boggart into a humorous shape) - 'Ridiculous' means 'absurd'.
• Sonorous (spell used to magnify a voice) - 'Sonorus' is Latin for 'loud'.
• Stupefy (spell used to make someone unconscious) - 'Stupefy' in English means 'dull the senses of; daze'.
• Veritaserum (truth potion) - 'Veritas' is Latin for 'truth' and a serum is a potion.