Come unwanted to someone's home, as in I told him to get out and never darken my door again. The verb darken here refers to casting one's shadow across the threshold, a word that occasionally was substituted for door. As an imperative, the expression is associated with Victorian melodrama, where someone (usually a young woman or man) is thrown out of the parental home for some misdeed, but it is actually much older. Benjamin Franklin used it in The Busybody (1729): "I am afraid she would resent it so as never to darken my doors again."