A tautology has two distinct meanings. In mathematical logic, it refers to a formula or assertion that is always true, regardless of the interpretation. For instance, “x=y or x≠y” is a tautology. Another example is the statement “either the ball is green, or the ball is not green,” which is always true, regardless of the color of the ball.
In everyday language, a tautology is a phrase that redundantly repeats the same idea in different words.
Some toponyms, which combine words from different languages, are often tautological. For example, Cheetwood (Lancashire) contains the words cę:to (Brittonic) + wudu (Old English), both with connotations of “wood, forest”. Similarly, Brill (Lincolnshire) is a combination of the Celtic word bre meaning “hill” and the English word “hill.” In the Pyrenees, the toponym Val d’Aran is a tautology, as “aran” means “valley” in Basque.
Montegibello in Sicily is another example, as it means “mountain mountain” in Latin and Arabic. In Algeria, the toponym Ain-Tala combines Arabic and Berber to mean “source source”. Other examples of tautological toponyms include Côtes-d’Armor in Brittany, which means “coast of coast” in French and Breton, and Dalsdalen in Norway, which means “valley’s valley” in Norwegian. Dasht-e Kavir in Iran means “desert desert”, while East Timor means “east east” in Indonesian and Malay. Minnehaha Falls in the US is named after the Dakota word for “waterfall”.