A warlock is a male practitioner of evil magic (distinguished from a wizard or sorcerer, whose magic may be benign). The most commonly accepted etymology derives warlock from the Old Englishwǣrloga meaning "oathbreaker" or "deceiver". However, in early modern Scots, the word came to be used as the male equivalent of witch (which can be male or female, but is used predominantly for females). From this use, the word passed into Romantic literature and ultimately 20th-century popular culture. A derivation from the Old Norsevarð-lokkur, "caller of spirits", has also been suggested; however, the Oxford English Dictionary discounts this due to the extreme rarity of the Norse word and the fact that forms without -k, consistent with the expected Old English etymology, are attested earlier than forms with -k.
^Old English wǽr-loʒa weak masculine (="traitor, enemy, devil, etc.") = Old Saxon wâr-logo weak masculine (=? "deceiver") (once, Hêliand 3817, in plural wârlogon applied to the Pharisees). The first element is probably Old English wǽr strong feminine (="covenant") = Old High German wâra (="truth"), Old Norse várar strong feminine plural ("solemn promise, vow") (cf. Vǽringi = "confederate, Varangian"); cf. Old Slavic. věra ("faith). This is a derivative from the adjective represented by Old English wǽr ("true") (once, Genesis 681; ? a. Old Saxon.) = Old Saxon, Old High German wâr ("true"): - Old Teutonic
wǣro-: - Pre-Teutonic
wāro- = Latin vērus. The second element (an agent-n. related to Old English léoʒan ("to lie belie, deny") occurs also in the similar comps. áþ-loʒa, tréow-loʒa (Old Saxon treulogo), wed-loʒa (Middle English wedlowe), ("an oath-breaker"), etc. - Oxford English Dictionary, (online) 2nd Edition (1989)
^McNeill, F. Marian, The Silver Bough: A Four Volume Study of the National and Local Festivals of Scotland, Glasgow: William Maclellan,1957, vol 1; also Chambers, Robert, Domestic Annals of Scotland, Edinburgh: 1861, and Sinclair, George, Satan's Invisible World Discovered, Edinburgh, 1871
^Cleasby, R.,Vigfusson, G. An Icelandic-English Dictionary, London, Macmillan, 1874
^Loewe, M., Blacker, C.Oracles and Divination, p.130 ("'Vardlokkur'...is related to the Scots dialect word 'warlock', wizard, and the meaning is thought to relate to the power to shut in or enclose"), London, George Allen & Unwin, 1981