The mobile nature of Scots society in the past required food that should not spoil quickly. It was common to carry a small bag of oatmeal that could be transformed into a basic porridge or oatcakes using a "girdle" (griddle). It is thought that Scotland's national dish, haggis, originated in a similar way: A small amount of offal or low-quality meat, carried in the most inexpensive bag available, a sheep or pig's stomach. It has also been suggested that this dish was introduced by Norse invaders who were attempting to preserve their food during the long journey from Scandinavia.