The act of crossing the fingers (i.e. middle finger over index finger) ‘for luck’, or to ward off ill luck (e.g. after walking under a ladder) is one of our most well-understood gestures, although we may often say it—‘I'll cross my fingers for you’— rather than actually carry out the action. Morris shows that the gesture is understood by some on mainland Europe but is only commonly found in Britain and parts of Scandinavia. Given its ubiquity in this country, it is surprising to find that the earliest reference found by Opie and Tatem only dated from 1912 (Leather, 1912: 88), where it is already linked to the ladder superstition. See thumb for an older gesture, of similar protective nature. One sphere in which crossed fingers are still taken seriously is in the school playground, used as a protective action to accompany a truce term to obtain temporary respite in a game. One of the popular explanations for the gesture's origin is that it dates from classical times when Christians were persecuted for their religion, and crossing the fingers was a secret way of invoking the cross. Given its late appearance, restricted distribution, and the fact that crossed fingers bear no relation to the shape of a cross, the explanation is completely unfounded.
See also CROSSING LEGS, FINGERS, GESTURES, THUMBS, TRUCE TERMS.
Opie and Tatem, 1989: 109;Morris, 1979: 15–24;Opie and Opie, 1959: 122–5, 142–53, 211–17.