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 and Wallachia) 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.