The name Cadeyrn originates from Old Welsh, specifically from the name Catigirn, which means 'battle king'. It is derived from the elements 'cat', meaning 'battle', and 'tigirn', meaning 'king' or 'monarch'. This name was notably borne by a 5th-century king of Powys in Wales, who was the son of Vortigern. The name embodies the qualities of leadership and martial prowess, reflecting the historical significance of its bearer.