Dardania is named after the Dardani, a tribe that lived in the region and formed the Kingdom of Dardania in the 4th century BC. The eastern parts of the region were at the Thraco-Illyrian contact zone. In archaeological research, Illyrian names are predominant in western Dardania (present-day Kosovo), while Thracian names are mostly found in eastern Dardania (present-day south-eastern Serbia). Thracian names are absent in western Dardania; some Illyrian names appear in the eastern parts. The correspondence of Illyrian names - including those of the ruling elite - in Dardania with those of the southern Illyrians suggests a "thracianization" of parts of Dardania. Celts were present in Dardania in 279 BC.