The name reestit mutton comes from the Scots language word reest, meaning to cure by drying or smoking.^[3][4] A wooden framework, called a reest, was traditionally placed across the rafters of a building,^[3] from which the mutton would traditionally be hung to dry with the aid of smoke from a peat fire.^[1]

Reestit mutton was traditionally prepared as a way of preserving mutton so that it could be eaten during winter. It is related to similar Scandinavian methods of drying meat, such as skerpikjøt.^[1] If prepared correctly reestit mutton can remain edible for up to four years.^[2]

Reestit mutton is prepared by soaking a leg or shoulder of mutton in brine. The correct ratio of coarse salt to water for the brine is achieved when a potato or egg will float in the solution.^[5] Some recipes also call for the addition of a small amount of sugar or saltpetre to the solution.^[6] The mutton is kept in the brine until the solution has reached all parts of the meat, which can take around three weeks.^[5] The meat is then hung to dry in proximity to a peat fire until the meat solidifies.^[5]

Reestit mutton has a salty flavour,^[7] which is also influenced by the peat smoke to which it is exposed when drying.^[1] The food is considered nostalgic by Shetlanders.^[1]

The first butcher to sell reestit mutton on a commercial basis in Lerwick, Shetland advertised it as having "an acquired taste that you acquire at the first taste".^[1]

Reestit mutton is commonly used as the basis for reestit mutton soup. The soup is made with tatties (potatoes), and is commonly served with bannocks - small savoury scone-like baked items.^[1] This dish is commonly associated with the Up Helly Aa fire festival. It can also be used as the filling of a reestit mutton pie.^[8]