This month, instead of one "word of the month," we have two. The words are "olive" and "Sahara." We chose these words in tandem not because olives trees are native to the Sahara region, but because they have something else in common besides geography. I'll leave you to ponder what that might be for a moment, and while you're pondering, I'll share their word origin stories.
The word "olive" comes to us from a lengthy sequence of words starting with Greek, then Latin, then Old French, and finally English. The word sequence for olive looks something like this:
elaion → elaia → oliva → olive
Are you curious to know what "eliaon" means? It means "oil." And doesn't that make sense? We get oil from olives (and by the way, it's very healthy stuff, too).
That's the word history for olive, but what about Sahara?
Well, Sahara has a much shorter word origin story; it comes to us directly from an Arabic word that means "desert" or "great desert."
So, have you figured out what these two words have in common? Here it is: They both are parts of common phrases that are linguistically redundant.
When you say "olive oil," you are, in a sense, saying "oil oil." And when you say "Sahara desert," you're really saying "desert desert."
Of course, both of these are acceptable phrases to use. The first one is acceptable because, even though it comes from a word that means "oil," the word "olive" doesn't actually mean "oil." Similarly, even though "Sahara" means "desert," it has also become a proper noun that refers to a specific region of the world, and the desert that region contains. Thus, "Sahara desert," while it may be frowned on in some circles, is still considered an acceptable usage. To satisfy my own doubts on the matter, I did a bit of searching online, and found -- among other reputable sites -- a National Geographic encyclopedia entry which refers to "The Sahara Desert."
I'm not going to argue with National Geographic on that one.