Cambria is a name for Wales, being the Latinised form of the Welsh name for the country, Cymru.[1] The term was not in use during the Roman period (when Wales had not come into existence as a distinct entity). It emerged later, in the medieval period, after the Anglo-Saxon settlement of much of Britain led to a territorial distinction between the new Anglo-Saxon kingdoms (which would become England) and the remaining Celtic British kingdoms (which would become Wales). Latin being the primary language of scholarship in Western Christendom, writers needed a term to refer to the Celtic British territory and coined Cambria based on the Welsh name for it.

The Welsh word Cymru (Wales), along with Cymry (Welsh people), was falsely supposed by 17th-century celticists to be connected to the Biblical Gomer, or to the Cimbri or the Cimmerians of Antiquity. In reality it is descended from the Brythonic word combrogi, meaning “fellow-countrymen”.[2] The term thus conveys something like “[land of] fellow-countrymen”. The use of Cymry as a self-designation seems to have arisen in the post-Roman Era, to refer collectively to the Brythonic peoples of Britain, inhabiting what are now Wales, Cornwall, Northern England, and Southern Scotland.[3] It came into use as a self-description probably before the 7th century[4]
and is attested in a praise poem to Cadwallon ap Cadfan (Moliant Cadwallon, by Afan Ferddig) c. 633.[5] In Welsh literature, the word Cymry was used throughout the Middle Ages to describe the Welsh, though the older, more generic term Brythoniaid continued to be used to describe any of the Britonnic peoples (including the Welsh) and was the more common literary term until c. 1100. Thereafter Cymry prevailed as a reference to the Welsh. Until c. 1560 the word was spelt Kymry or Cymry, regardless of whether it referred to the people or the country.[6] The Latinised form Cambria was coined in the Middle Ages, and was used regularly by Geoffrey of Monmouth.