What's In a Name? -- Now Updated For Book 6!

Waffling, Adalbert - author of History of Magic and Magical Theory

Adalbert is one of many saints mentioned in the HP books. He was a Bohemian churchman, known as the Apostle of the Prussians.
"Waffling" is "to waver in mind, will, or feeling; to hesitate in choice of opinions or courses" (M-W), which makes a good name for a theorist.

Wagga Wagga Werewolf - supposedly banished by Gilderoy Lockhart

"Wagga Wagga" is a place in New South Wales, Australia, and means "place of many crows" (go figure... thanks to Storm Stanford on HP4GU) Incidentally, it's fairly close to the city of Lockhart.

Walpurgis, Knights of - See "Knights of Walpurgis"

Wattlebird - a password into the Gryffindor common room

Weasley, Arthur - father of the Weasley family

According to Ivy, "Arthur is a possible reference to King Arthur. The World Book says, 'There are two versions of the events that led to Arthur's death. Both say he fought a war against Roman emporer Lucius.'" Interesting...

Weasley, Ginny (Ginevra) Molly - Ron's little sister

"Ginevra" is the Italian word for "juniper," which in herb lore is used for purification. Meanwhile, we also have a character named Lily, which symbolizes purity. Someone has an Oedipus complex.
Before JKR revealed Ginny's true name, many fans theorized that Ginny was short for Virginia or Guinevere. All is not lost! "Ginevra" is a German equivalent of "Guinevere," and the connection from Ginevra to juniper to purity to "Virginia" isn't too farfetched, either. Fan Elizabeth Whitten notes "As Frederick, William, Charles, Arthur, and George were all famous kings, it's possible that Ginny's name derived from Queen Elizabeth I, known as "The Virgin Queen" (hence "Virginia")." Guinevere, on the other hand, derives from the Welsh legend Gwenhwyfar, who was a shape changer. Do we have an animagus in our future? Probably not, as this is getting to be pretty farfetched etymology-wise, but it's still fun to grasp at straws!

Weasley, Molly - mother of the Weasley family

Her name is clearly derived from "mollycoddle", which means "to surround with an excessive or absurd degree of indulgence and attention." That's our Molly!

Weasley, Ron (Ronald) Bilius - Redhead friend of Harry and Hermione, former owner of "Scabbers".

In Arthurian legend, "Ron" is the name of King Arthur's trusty ebony spear. The name is derived from Rhongomynyad (cutting-spear). (more)

Weasley, Percy Ignatius - straight-laced, ambitious, former Head Boy, and fellow Weasley.

According to Positively Percy , "Percival" was a name reserved only for the upper class of Britain in the days of the Monarchy. Later, the British commoners were allowed to use a version of this name (previously, they would have been punished). This variant was "Percy"; Percival itsself still off-limits. By being named "Percy", the name plays off our Percy's family roots as a "poor commoner". Additionally, Sir Percival was one of King Arthur's knights.
Ignatius is Latin for firery, ardent. St. Ignatius was a cleric who was obsessed with money and power, until he was captured and injured by the enemy, and he had a change of heart while being held prisoner. Hopefully, this indicates that our Percy will have a change of heart.

Weasley's Wizard Wheezes - Fred and George's future joke shop

"Wizard wheeze" is a somewhat common expression meaning "a clever scheme or joke." I'm not sure where the phrase originated, as I've spotted it in Molesworth, Terry Pratchett, and quite a few articles and USENET posts.

Weird Sisters - a famous wizarding music group

The original "Weird Sisters" were the three witches in Shakespeare's Macbeth. The term has also since been used for the three Fates, women that spin threads of life in Greek and Roman mythology.

Werewolf - wizards that turn into wolves at the full moon

In popular folklore, a man who is transformed, or who transforms himself, into a wolf in nature and appearance under the influence of a full moon. According to legend, werewolves can be killed by silver objects such as silver arrows and bullets, but there is no indication that JKR's werewolves share this "allergy."

Widdershins, Willy - arrested over a matter of regurgitating toilets

Wingardium Leviosa - Spell used to lift objects

Winged Horse - just what it sounds like

Witherwings - Buckbeak's new name

"Wither-" refers to his horse-half. The withers are the high part of the back of a horse or similar animal, located between the shoulder blades. "Wings" refers to his bird half. In short, the formula is indentical to his previous name of Buckbeak.

Wizengamot - Wizarding jury

Tom Stermitz and Steve Vander Ark: The Wizengamot gets its name from the Witan, also known as the Witenagemot, from Anglo-Saxon England. Witan is defined as "an assembly of higher ecclesiastics and important laymen, including king's thegns, that met to counsel the king on matters such as judicial problems."

Wolfsbane - See "Aconite"

Wood, Oliver - former Gryffindor Quidditch captain

Like Marcus Flint, the Slytherin captain, his last name is a raw material. "Wood" is also an archaic English word for "violently mad," which ties in nicely with his "manic enthusiasm" for Quidditch.

Wormtail - Pettigrew's nickname at Hogwarts, and now his "official" death eater nickname.

The name "Wormtail" is too close to Tolkien's "Wormtongue" (Lord of the Rings) for the two not to be connected! Wormtongue was Theoden's corrupt advisor, who joined Sauruman.