Caledonia is the Latin name given by the Romans to the land in today's Scotland north of their province of Britannia, beyond the frontier of their empire. The etymology of the name is probably from a P-Celtic source. Its modern usage is as a romantic or poetic name for Scotland as a whole. The original use of the name, by Tacitus, Ptolemy, Lucan and Pliny the Elder, referred to the area (or parts of the area) also known as Pictavia or Pictland north of Hadrian's Wall in today's Scotland. The name may be related to that of a large central Pictish tribe, the Caledonii, one amongst several in the area and perhaps the dominant tribe, which would explain the binomial Caledonia/Caledonii. The name of the Caledonians can be found in toponymy, such as Dùn Chailleann, the Scottish Gaelic word for the town of Dunkeld meaning "fort of the Caledonii", and possibly in that of the mountain Sìdh Chailleann, the "fairy hill of the Caledonians".
According to Historia Brittonum the site of the seventh battle of the mythical Arthur was a forest in what is now Scotland, called Coit Celidon in early Welsh. Traces of such mythology have endured until today in Midlothian: near the town centre of Edinburgh stands an old volcanic mountain called Arthur's Seat. There are other hypotheses regarding the origin of Caledonia (and Scotia). According to Moffat (2005) the name derives from caled, the P-Celtic word for "hard". This suggests the original meaning may have been "the hard (or rocky) land" although it is possible it meant "the land of the hard men".