Describing a secret or undercover operation. The term dates from seventeenth-century Spain, and the popular swashbuckling plays of Lope de Vega and Pedro Calderón de la Barca, filled with duels, intrigue, and betrayal. They were referred to as comedias de capa y espada, which was variously translated as “cloak-and-sword” or “cloak-and-dagger plays.” Somewhat later, in the nineteenth century, the term began to be applied to various kinds of romantic intrigue, and still later, to espionage. The idea of concealment was, of course, much older, and indeed, Chaucer wrote of “The smyler with the knyf under the cloke” (The Knight’s Tale).