The word Celt is derived from Keltoi, the name given to these people by Herodotus and other Greek writers. To the Romans, the Continental Celts were known as Galli, or Gauls; those in the British Isles were called Britanni. In the 4th century BC , the Celts invaded the Greco-Roman world, conquering northern Italy, Macedonia, and Thessaly. They plundered Rome in 390, sacked Delphi in 279, and penetrated Asia Minor, where they were known as Galatians. The Cisalpine Gauls of northern Italy were conquered by the Romans in the 2nd century BC; Transalpine Gaul (modern France and the Rhineland) was subdued by Julius Caesar in the 1st century BC, and most of Britain came under Roman rule in the 1st century AD. In the same period, the Celts of central Europe were dominated by the Germanic peoples. In medieval and modern times the Celtic tradition and languages survived in Brittany (in western France), Wales, the Scottish Highlands, and Ireland.