The English words "Wales" and "Welsh" derive from the same Germanic root (singular Walh, plural Walha), which was itself derived from the name of the Celtic tribe known to the Romans as Volcae and which came to refer indiscriminately to all Celts. The Old English-speaking Anglo-Saxons came to use the term Wælisc when referring to the Celtic Britons in particular, and Wēalas when referring to their lands. The modern names for some Continental European lands (e.g. Wallonia, Wallachia and Valais) and peoples (e.g. the Vlachs via a borrowing into Old Church Slavonic) have a similar etymology.
Historically in Britain, the words were not restricted to modern Wales or to the Welsh but were used to refer to anything that the Anglo-Saxons associated with the Britons, including other non-Germanic territories in Britain (e.g. Cornwall) and places in Anglo-Saxon territory associated with Celtic Britons (e.g. Walworth in County Durham and Walton in West Yorkshire), as well as items associated with non-Germanic Europeans, such as the walnut.
The modern Welsh name for themselves is Cymry, and Cymru is the Welsh name for Wales. These words (both of which are pronounced [ˈkəm.rɨ]) are descended from the Brythonic word combrogi, meaning "fellow-countrymen". The use of the word Cymry as a self-designation derives from the location in the post-Roman Era (after the arrival of the Anglo-Saxons) of the Welsh (Brythonic-speaking) people in modern Wales as well as in northern England and southern Scotland (Yr Hen Ogledd) (English: The Old North). It emphasised that the Welsh in modern Wales and in the Hen Ogledd were one people, different from other peoples. In particular, the term was not applied to the Cornish or the Breton peoples, who are of similar heritage, culture, and language to the Welsh. The word came into use as a self-description probably before the 7th century.
It is attested in a praise poem to Cadwallon ap Cadfan (Moliant Cadwallon, by Afan Ferddig) c. 633. 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 their homeland.
The Latinised forms of these names, Cambrian, Cambric and Cambria, survive as lesser-used alternative names for Wales, Welsh and the Welsh people. Examples include the Cambrian Mountains (which cover much of Wales and gave their name to the Cambrian geological period), the newspaper Cambrian News, and the organisations Cambrian Airways, Cambrian Railways, Cambrian Archaeological Association and the Royal Cambrian Academy of Art. Outside Wales, a related form survives as the name Cumbria in North West England, which was once a part of Yr Hen Ogledd. The Cumbric language, which is thought to have been closely related to Welsh, was spoken in this area until becoming extinct around the 12th century. This form also appears at times in literary references, as in the pseudohistorical "Historia Regum Britanniae" of Geoffrey of Monmouth, where the character of Camber is described as the eponymous King of Cymru.