Definition: The spoon was the wooden-shafted club in (primarily) pre-20th Century golf history that is most equivalent to today's 3-woods. A modern 3-wood is not a spoon, however. Spoons were called that because their clubfaces were concave (shaped like a spoon, in other words). But in appearance, loft and purpose, the spoon is the antique golf club that most resembles today's 3-woods.
Source: British Golf Museum