Yorkshire is a historic county of England, centred on the county town of York. The region was first occupied after the retreat of the ice age around 8000 BC. During the first millennium AD it was inhabited by celtic Britons and occupied by Romans, Angles and Vikings. The name comes from "Eborakon" (c. 150) an old Brythonic name which probably derives from "Efor" or "the place of the yew-trees." Many Yorkshire dialect words and aspects of pronunciation derive from old Norse due to the Viking influence in this region. The name "Yorkshire", first appeared in writing in the Anglo-Saxon Chronicle in 1065. It was originally composed of three sections called Thrydings, subsequently referred to as Ridings.