This is the Pictish symbol known as the Crescent & V-Rod. It appears on various carved stones in Scotland, usually accompanied by one or more other symbols. But what does it mean?
Various theories about the Pictish symbols have been proposed, each with its supporters and critics. The one I cautiously lean towards is the idea that they represent personal names, and that where two symbols appear as a pair on a particular stone they commemorate a person “X, son of Y” (or Z, daughter of Y). One supporter of this theory is W.A. Cummins who has suggested that the Crescent & V-Rod – the symbol appearing most frequently on the stones – might represent Brude – the name appearing most frequently in the Pictish king lists.
The abstract design of the symbol has been seen by some people as an arrow breaking on a shield, by others as a crescent moon with a geometrical instrument like a pair of dividers. We will never know its real meaning but the idea that this and other symbols were used by the Picts in a kind of pictorial alphabet for words or names, like ancient Egyptian hieroglyphics, is the one I vote for at the moment.
W.A. Cummins, The Picts and their symbols (Stroud, 1999)