The Caledonians (; or ; , Kalēdōnes) or the Caledonian Confederacy were a Brittonic-speaking (Celtic) tribal confederacy in what is now Scotland during the Iron Age and Roman eras. The Greek form of the tribal name gave rise to the name Caledonia for their territory. The Caledonians were considered to be a group of Britons, but later, after the Roman conquest of the southern half of Britain, the northern inhabitants were distinguished as Picts, thought to be a related people who would have also spoken a Brittonic language. The Caledonian Britons were thus enemies of the Roman Empire, which was the state then administering most of Great Britain as the Roman province of Britannia. The Caledonians, like many Celtic tribes in Britain, were hillfort builders and farmers who defeated and were defeated by the Romans on several occasions. The Romans never fully occupied Caledonia, though several attempts were made. Nearly all of the information available about the Caledonians is based on predominantly Roman sources, which may be biased. Peter Salway assumes that the Caledonians would have been Pictish tribes speaking a language closely related to Common Brittonic, or a branch of it augmented by fugitive Brythonic resistance fighters fleeing from Britannia. The Caledonian tribe, after which the historical Caledonian Confederacy is named, may have been joined in conflict with Rome by tribes in northern central Scotland by this time, such as the Vacomagi, Taexali and Venicones recorded by Ptolemy. The Romans reached an accommodation with Brythonic tribes such as the Votadini as effective buffer states. Etymology According to German linguist Stefan Zimmer, Caledonia is derived from the tribal name Caledones (a Latinization of a Brittonic nominative plural n-stem Calīdones), which he etymologises as "possessing hard feet" ("alluding to standfastness or endurance", from the Proto-Celtic roots" *kal- "hard" and *φēdo- "foot"). The singular form of the ethnic name is attested as Caledo (a Latinization of the Brittonic nominative singular n-stem *Calidū) on a Romano-British inscription from Colchester. History In AD 83 or 84, led by Calgacus, the Caledonians' defeat at the hands of Gnaeus Julius Agricola at Mons Graupius is recorded by Tacitus. Tacitus avoids using terms such as king to describe Calgacus and it is uncertain as to whether the Caledonians had single leaders or whether they were more disparate and that Calgacus was an elected war leader only. Tacitus records the physical characteristics of the Caledonians as red hair