Short answers, pulled from the story.
Modern linguists base their analysis on comparative Celtic methods and suggest the land of Caledonia comes from the tribal name Caledones. This term is a Latinization of a Brittonic nominative plural n-stem that may mean possessing hard feet alluding to standfastness or endurance.
Tacitus records that in AD 83 or 84 the Caledonians led by Calgacus were defeated at Mons Graupius by Gnaeus Julius Agricola. Roman sources describe red hair and long limbs among these people but avoid calling Calgacus a king.
The Caledonians inflicted fifty thousand Roman casualties through attrition and guerrilla warfare tactics before eventually ceding territory to Rome. Cassius Dio recorded in 209 that the Caledonians surrendered to emperor Septimius Severus following his personal military expedition north of Hadrian's Wall.
Archaeological evidence suggests most Caledonians north of the Firth of Forth lived in villages without fortifications using timber or stone houses. Those near the Western coast more often utilized dry stone construction methods instead.
A great victory over Caledones and others appears in Panegyrici Latini Vetares VI VII vii 2 marking first recorded use of term Pict for area tribes. This event occurred when Constantius Chlorus re-invaded northern lands of Britain in 305 though sources remain vague about penetration into far north regions.