What is "vortimer"

Vortimer ( Old Welsh Guorthemir, ), also known as Saint Vortimer (, "Vortimer the Blessed"), is a figure in British tradition, a son of the 5th-century Britonnic ruler Vortigern. He is remembered for his fierce opposition to his father's Saxon allies. In Geoffrey of Monmouth's Historia Regum Britanniae, he overthrows his father and reigns as King of Britain for a brief period before his death restores Vortigern to power.