What do the River Avon, the Gobi Desert, and the La Brea Tar Pits have in common? Redundancy.
There’s an old story about an explorer arriving in a new territory. He points to a mountain (or some other geographic feature) and asks a local what it’s called. The local gives him a name, say “X,” and from then on the explorer calls it Mount X. Except the local was just telling him the word “mountain” in the local language. Translated, the name is now “Mount Mountain”. This is a polyglot tautology.
I’ve seen this story often enough, and applied to enough places, that it seems likely some version has played out in reality multiple times. Invaders, colonists, or settlers impose their own naming conventions over the top of the existing ones. We are left with the same word, or at least one with a similar meaning, doubling up.
The Gobi Desert and the Sahara Desert are good examples. “Gobi” (well, “govi”) is apparently Classical Mongolian for “desert.” Likewise, “ṣaḥra'” is the Arabic word for “desert.” So calling these places the Sahara Desert or the Gobi Desert is redundant. (And, indeed, it makes more sense to just call it the Sahara.)
The River Avon, running through Shakespeare’s hometown Stratford-Upon-Avon, is another example. “Avon” in an ancient Celtic language means “river” – so the River Avon is more properly the River River. The La Brea Tar Pits manage to be redundant in two ways: La Brea is Spanish for “the tar” – so the La Brea Tar Pits effectively mean “the the tar tar pits.”
There are hundreds more examples out there. One meme currently doing the rounds points out that Torpenhow Hill in England is a quadruple tautology. “Tor” (Old English), “pen” (Old Welsh), “haugr” (Old Norse), and “hill” (English) together make this place “Hill hill hill hill.” Alas, this one is too good to be true: the actual place isn’t called a hill, and while “tor” is an Old English word it also features in Old Welsh – the “tor” and “pen” together indicating the top of a hill.
Oh, and apparently the locals pronounce Torpenhow “tre-penna.”