Warlocks are, among historic Christian traditions, said to be the male equivalent of witches (usually in the pejorative sense of Europe's Middle Ages), and were said to ride pitchforks instead of broomsticks.
In some pop culture TV shows like Buffy the Vampire Slayer and Bewitched warlocks are male witches. In the TV show Charmed a warlock is an evil witch, a "traitor to an oath" who steals other witches' powers, while any good male witch featured retains the title "witch"
The normal etymology derives warlock from the Old English wærloga meaning deceiver, or "oathbreaker". However, one source suggests that the word may come from the Old Norse varð-lokkur, "caller of spirits". Varðlokkur is also translated by some as 'ward-locks' or 'protections', and is an invocation chant used in spæ (scrying).
A highly speculative etymology interprets 'wærloga' as 'the man of the logs' alluding to the small pieces of wood the Anglo-Saxon and Scandinavian priests and wise men (called bards and skalds, respectively) used to divine by means of the runes. This etymology seems to have been created to support neopagan beliefs about the past, inasmuch as warlock then appears to be a slang word of Christian coinage pejoratively used for those who remained Pagan and practising the art of the runes. However, its dependence upon sarcastic Christians referring to small pieces of wood as 'logs' makes it extremely unlikely, especially since the etymological roots of 'log' are believed to refer to felled trees or equally massive objects.
Warlocks in books and comics
In the Sword of Shannara books by Terry Brooks, the Warlock Lord was Brona, a druid who delved too deeply and quickly into forbidden knowledge and was corrupted by it.
Christopher Stasheff wrote a series of science fiction/fantasy novels about a technological warlock, beginning with The Warlock in Spite of Himself.
Warlocks are an alien race in the comic book series Nemesis the Warlock, which was adapted into a Commodore 64 video game. There, a warlock possesses the ability to alter his body to become different objects, and he finds sustenance by absorbing the energy from organic materials, leaving a lifeless husk in its wake.
In JK Rowling's Harry Potter, Albus Dumbledore is Chief Warlock of the Wizengamot. As Dumbledore is one of the chief protagonists of the series, the term seems to have no negative connotation here.
In Mollie Hunter's Thomas and the Warlock, Hugo Gifford is a wicked and fearsome warlock with black eyes who casts no shadow due to a trick he played on the devil.
In the book "Warlock" by Wilbur Smith, the Egyptian slave Taita becomes "The Warlock", after spending years in the desert, studying and praying.
Warlocks in games
In the Shadowgate series, the Warlock Lord, Talimar, betrayed the Circle of Twelve and summoned the Behemoth, but was unable to control it.
In the Warcraft series, warlocks are evil sorcerers, drawing their powers from demonic sources in exchange for their souls. In World of Warcraft, a warlock is a cloth-wearing spellcasting character class. It can summon and enslave demons to fight alongside itself, although those requiring enslavement can turn on the warlock and his allies. The warlock plays a valuable damage dealing class role, he can cast curses, and also play a minor support role by creating healthstones and soulstones (in order to let other players reincarnate from it).. The warlock is a master of powerful curses that have the ablity to deal damage over time (DOT) and can also do some direct damage to its enemies by, for example, burning their souls.
There was a game called Warlock for the Sega Genesis that involved a powerful warlock attempting to gain a series of rune stones that the player (a Druid) is pressed to seek out first. The game is known for its extreme difficulty and unique yet solid control scheme.
In the Shadowbane MMORPG, warlocks are psychokinetic telepaths that attack and defend themselves using only the will of their minds, utilizing self-awareness and intense focus where other classes would rely on magic, armor, or physical strength and dexterity. In Shadowbane, Warlocks can be mage or fighter-based, and are known somewhat for their rare damage type, (mental), and for their ability to take on a wide variety foes without the help of others.
In Dark Age of Camelot, the warlock is a spellcasting character class in the realm of Midgard. Norse, Frostalf, and Kobold are the races capable of becoming a warlock. Warlocks in DAoC are unique casters in their ability to cast and land two spells at once, although they trade longer casting times for this ability. Their other defining trait is the ablitity to "chamber" spells: they can cast and hold spells to trigger for instant effect.
In Battle Realms, the warlock represents the "flower" of the Lotus Clan. The Lotus Clan's religion centers on three brothers that tend the Yin side of the Tree of Life, the Tree of Corruption. The Lotus Clan studies the Forbidden Path, which is about death and corruption. Since being a warlock means mastering this path, they are immune to the effects of aging and are near-immortal.
In Tactics Ogre, a Warlock was a scholarly type of magician who researched ancient languages. They could boost the power of nearby golems and help troops out with support magic, slow down enemies with status-inducing magic, or use Dragon Magic to attack all enemies at once. They were very fragile and easily killed, however. In Tactics Ogre: The Knight of Lodis, Warlocks were changed from a pure spellcaster to a hybrid of an attacker and a spellcaster. Their preferred weapon of choice was a sword and they could use their ability, Barren Soul, to attack an enemy with a sword of the opposite element. (It did not work on enemies of the Virtue or Bane elements, however) If they weren't aiding the front lines, they were in the back slowing down the enemy with status inducing spells or aiding allies with spells.
In Dungeons & Dragons, Warlocks are an alternative arcane spell-casting Core Class introduced in the Complete Arcane sourcebook. Warlocks do not learn or gain spells like other mages, instead they have access to a small pool of Invocations, special Spell-Like Abilities that suffer some of the drawbacks of conventional spells, such as the ability to be interrupted and the requirement of somatic components. They also have other special abilities, such as their primary weapon; the Eldritch Blast. What makes them a match of other mages is that their Invocations can be used an unlimited amount of times per day, so they do not run the risk of running out of spells. Warlocks gain their power through ties, forged intentionally or unintentionally, with alien, chaotic forces, primarily fiends.
In Rifts, Warlocks are spellcasters who join into a pact with Elementals, and bind themselves to their power. Warlocks have a kind of brotherhood with both Elementals and other Warlocks, and will treat each other cordially and with respect, even if they're about to battle each other.
Warlocks in film and television
The Warlocks was the original name of the San Francisco-based 1960's rock band that came to be known as the Grateful Dead.