A cairn is a man-made pile (or stack) of stones. The word cairn comes from the Scottish Gaelic: càrn (plural càirn). Cairns are found all over the world in uplands, on moorland, on mountaintops, near waterways and on sea cliffs, and also in barren desert and tundra areas. They vary in size from small stone markers to entire artificial hills, and in complexity from loose, conical rock piles to delicately balanced sculptures and elaborate feats of megalithic engineering. Cairns may be painted or otherwise decorated, whether for increased visibility or for religious reasons.
The word cairn derives from Scots cairn (with the same meaning), in turn from Scottish Gaelic càrn, which is essentially the same as the corresponding words in other native Celtic languages of Britain and Ireland, including Welsh carn (and carnedd), Irish carn, and Cornish karn or carn. Cornwall (Kernow) itself may actually be named after the cairns that dot its landscape, such as Cornwall’s highest point, Brown Willy Summit Cairn, a 5 m (16 ft) high and 24 m (79 ft) diameter mound atop Brown Willy hill in Bodmin Moor, an area with many ancient cairns. Burial cairns and other megaliths are the subject of a variety of legends and folklore throughout Britain and Ireland. In Scotland, it is traditional to carry a stone up from the bottom of a hill to place on a cairn at its top. In such a fashion, cairns would grow ever larger. An old Scottish Gaelic blessing is Cuiridh mi clach air do chàrn, “I’ll put a stone on your cairn”. In Highland folklore it is believed that the Highland Clans, before they fought in a battle, each man would place a stone in a pile. Those who survived the battle returned and removed a stone from the pile. The stones that remained were built into a cairn to honour the dead. Cairns in the region were also put to vital practical use. For example, Dún Aonghasa, an all-stone Iron Age Irish hill fort on Inishmore in the Aran Islands, is still surrounded by small cairns and strategically placed jutting rocks, used collectively as an alternative to defensive earthworks because of the karst landscape’s lack of soil.