This name means “land of the Britons”. Britannia derives from the Greek Πρεταννικαὶ Νῆσοι (Pretannikai Nesoi) used by Pytheas of Marseilles, a Greek geographer and explorer, who had circumnavigated Britain between 330 and 320 BC and described various islands in the North Atlantic to the extreme Thule (probably Iceland or the Shetland Islands). Pytheas described Thule as the northernmost part of Prettanikḗ (Πρεττανική) or Pretannikaí (Πρεταννικαὶ), his term for the entire group of islands in the far north-west. There is a possibility that the term may derive from the Celtic “*Pritani “, meaning “Picts”. In AD 43 the Roman Empire began its conquest of the island, establishing a province they called Britannia, which came to encompass the parts of the island south of Caledonia (Scotland). The native Celtic inhabitants of the province are known as the Britons. In the 2nd century, Roman Britannia came to be personified as a goddess, armed with a trident and shield and wearing a centurion's helmet.