The history of the term boudinage, the varieties that have been observed in Perthshire, Scotland (barrel-shaped and lozenge-shaped), and the theories of formation are discussed. The possibility that the type of boudinage produced is directly related to the rigidity differential of the material and the enclosing rocks is discussed and the engineering term "necking," denoting a thinning rather than tensional cracking, is suggested for this type of behavior.