Apotropaic

apotropaic [ap-uh-truh-PAY-ik]
adj. intended to ward off evil

[From Greek apotrópaios ("averting evil), combining apo- ("apart from") + -trope ("that which turns")]

In a pre-scientific age, the mysterious "evil" was credited with all sorts of misfortune: disease, storms, loss of money, mental illness, crop failure, war, etc. Much of religion, whether monotheistic or polytheistic, seems to have been created to explain evil and ward it off. Despite the fact that there are generally good scientific explanations for "evil" -- we know, for example, how and why hurricanes form and can predict with some accuracy where they will make landfall -- there are still morons all over the world who live by superstitions and ascribe "evil" to supernatural causes. Some wear amulets ("small objects worn to ward off evil, harm, or illness or to bring good fortune"), while others carry talismans ("a stone, ring, or other object, engraved with figures or characters supposed to possess occult powers and worn as an amulet or charm"). In voodoo, followers build small shrines of the occult to ward off evil. In Shinto, large gates (torii) are designed to keep out evil. In Islam, Muslims wear an "evil eye" in order to protect themselves.

In Slate, Christopher Hitchens decries the application of euphemisms to bad actors, including supernatural demons:

In a media world where Bin Laden's murderous surrogates in Iraq can be given a homely moniker, perhaps we shouldn't be surprised. As a novel about the Nazi era has recently reminded us, the Furies of antiquity were so much dreaded that they were sometimes apotropaically named "the Kindly Ones," or Eumenides.