Excavations have found evidence that the hill fort was occupied by 1000 BC, in the Bronze Age. The ramparts seem to have been built and rebuilt in three phases. 296 individual huts floors have been identified within the fort, suggesting a population of around 2000, and making it one of the largest known in Scotland from this period. The hill fort is thought to have been the capital of the Selgovae Celtic Tribe, who lived in upper Tweeddale prior to the arrival of the Romans.

In the 1st century AD the Roman army built the massive fort of Trimontium at Newstead, named after the three peaks, at the foot of the hill on the bank of the River Tweed. In association with this fort they constructed a signal tower with a tiled roof in a 15 m diameter enclosure built on the summit of Eildon North Hill, similar to those found on the Gask ridge. The hill fort may have been abandoned by this time, as Roman archaeological finds uncovered during excavation of the site in 1986 all overlaid native finds. The tower was thought to have been constructed out of timber during the Flavian period, with a later tower being constructed out of stone during the reign of Emperor Antoninus Pius. Finds including Roman coins and pottery have suggested that some of the house platforms were again in use in the 2nd to 4th century.

There is some evidence that prehistoric peoples regarded the Eildon Hills as a holy place and scholars believe they may have been a place of ceremonial gatherings. There are several holy springs around the base of the hills, now dedicated to Christian saints, but probably originally sacred to Celtic deities.

They were once known as Eldune, derived from the 12th-century Simeon of Durham who referred to them as Eldunum. The final part of the word is Old English dun, meaning a rounded hill, while the first part has been variously etymologized as Brittonic eil (referring to a fenced enclosure) or Old English ǣled (“fire”) or ǣlǣte (“empty place”).

Sites near Eildon Hill