What does Boxing Day have to do with boxing?
(From George Bush's "voodoo economics") The use by guess or cookbook of an obscure or hairy system, feature, or algorithm that one does not truly understand. The implication is that the technique may not work, and if it doesn't, one will never know why. Almost synonymous with black magic, except that black magic typically isn't documented and *nobody* understands it.
Compare magic, deep magic, heavy wizardry, rain dance, cargo cult programming, wave a dead chicken.