"And not actually a king either, assuming he existed."
From the OED:
" In OE. the title appears first as the name of the chiefs of the various Anglian and Saxon ‘kins’, tribes, or clans, who invaded Britain, and of the petty states founded by them, as well as of the native British chiefs or princes with whom they fought, and of the Danish chiefs who at a later time invaded and occupied parts of the country. Among the Angles and Saxons the kingship was not strictly hereditary, according to later notions; but the cyning was chosen or accepted in each case from a recognized kingly or royal cynn or family (usually tracing its genealogy up to Woden). With the gradual ascendancy and conquests of Wessex in the 9th and 10th c., the king of the West Saxons became the king of the Angelcynn, Angelþéode, or English (Angligenarum, gentis Angligenæ, Anglorum), and the tribal kings came to an end. But there still remained a King of Scotland, and several petty kings in Ireland. In European and other more or less civilized countries, king came to be the title of the ruler of an independent organized state called a kingdom; but in mediæval times, as subsequently in the German Empire, some kings were really or nominally subordinate to the Emperor (as ostensibly representing the Roman Cæsar or Imperator), and a King was held to rank below an Emperor. In reference to ancient times the name is applied, like L. rex, Gr. βασιλεύς, Heb. melek, to the more or less despotic rulers not only of great dominions like Assyria, Persia, Egypt, but of petty states or towns such as Jericho, Ai, Mycenæ, Ithaca, Syracuse, and Rome. It is still applied to the native rulers of petty African states, towns, or tribes, Polynesian islands, and the like. "