This symbol can be found in a number of passage tombs in Brittany, including Mané Hroeck, Mané Rutual, Mané Lud, Gavrinis. The backstone of the passage tomb 'Table des Marchands' in Locmariaquer shows a number of this symbol. Further the capstone shows a crook next to an axe carving.
The initial name 'crook' was given to this symbol, since it resembles the shape of a shepherd's crook. In Egypt this was a symbol of power and it was also adopted by Christianity (bishop's crook).
However, recently this symbol is thought to be a depiction of a weapon or projectile, similar to a boomerang. This seems to be supported by the depiction of the symbol next to a hafted axe on the capstone of the Table des Marchands.
In this case the 'crook' would been a symbol of power like the axe depictions.