(A). A shelf over a fire-place, originally used for drying clothes.
“Around the spacious cupola, over the Italian fire-places, is a ledge to which are affixed pegs, on which postillions hung their wet clothes to dry. We call the shelves over the fire-places `mantel-pieces,' but we no longer hang our mantles on them to dry.” —Memoirs of Col. Macaroni.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894