Mmm, citrusy good. But I think I just broke a tooth.

Dear Word Detective: I read the ingredients printed on a package of taco shells (ground corn, lime, vegetable shortening). I’ve heard (well, read) different views on what form of “lime” is meant in tortilla recipes, but I got to wondering: Is the “lime” in limestone (dull, grey, sedimentary rock) in any way related to the “lime” that is a bright, green, citrusy addition to a good gin and  tonic? And for that matter, how do “limey” and “blimey” work into the mix? — Danny.

Gin and tonic, eh? I’ve always said that if I were to take up drinking, it’d be gin and tonics, the only mixed drink that ever tasted good to me. There’s also the odd fact that when I was very small, there was someone on our road who drank a lot of Gilbey’s gin and always threw the frosted glass bottles on our lawn. I thought those bottles were incredibly cool, but my parents wouldn’t let me collect them. Probably afraid I’d take a few dozen to “Show and Tell” day at my school.

I must admit that your first two sentences, about taco shells containing lime, intrigued me, and I subsequently spent a good hour or so researching the question of what sort of “lime” is being dished up by Taco Bell. It turns out that some tortilla recipes do call for the juice of the “lime” fruit, but that’s not the main sort of “lime” in taco-land.

It all begins with the mineral limestone, a hard, plentiful form of calcium carbonate often used to build large buildings and similar durable structures. (Fun fact: The crystalline form of limestone is marble.) Limestone is also used to make calcium oxide, also known as “quicklime,” “burnt lime,” or simply “lime.”  This “lime” is made by subjecting limestone to very high heat in a kiln; the result, quicklime, is an extremely caustic substance widely used in industry (and in old murder mysteries to dispose of the body). Incidentally, back in the 19th century, before the widespread introduction of electric lighting, theaters used “limelight,” a brilliant white light produced by heating quicklime, as stage lighting. The term “limelight” is still used as a metaphor for “public attention,” usually positive (“The beauty of his person … helped to throw the limelight upon him,” 1908).

Interestingly, the English word “lime” behind all this comes from Germanic roots meaning “to smear,” which makes more sense when you find that “lime” was originally used to mean a sticky substance made from holly bark and used to trap birds. The change in meaning came about because “quicklime” was often a component of mortar, which makes bricks stick together.

So “quicklime” is pretty nasty stuff and would be a bad choice as a food ingredient, but if you mix it the right way with water, you get calcium hydroxide, also known as “slaked lime,” which is much less scary and plays all sorts of useful roles in industry (it’s used in depilatories, for instance). In food preparation, slaked lime is used as a calcium supplement, in pickling, and, here ya go, to make the corn meal flour in tortillas stick together better. So that’s the lime on the taco shell package (which, as I said, may also mention lime fruit juice).

Meanwhile, back at your gin and tonic, the name of the citrus fruit resembling a green lemon called a “lime” is from a completely unrelated source. “Lime” came from the Old French “limon,” which at that time meant citrus fruit in general, including both lemons and limes. Portuguese, French and Spanish have similar words, and all are probably of Middle Eastern origin (Persian “limun,” Arabic “lima,” etc.).

“Limey” (originally “lime-juicer”) as a colloquial and mildly derogatory term for a British person goes back to the 19th century Royal Navy, when sailors were required to drink lime juice at sea to ward off scurvy (caused by a lack of vitamin C). “Blimey” and “gorblimey,”  stereotypical lower-class British expressions of distress or astonishment, are corruptions of, respectively, “Blind me!” and “God blind me!” Both date to the 19th century, are now usually heard only in films, and have nothing to do with limes.