Well, now, here’s a word to wax eloquent on. We can start with how it’s said. That might not be self-evident, especially when the usual ways of saying borrowed Latin words don’t gibbous the right answer. Yes, the g is [g], at the back of the mouth, not at the tip of the tongue, and so it makes a balancing pair with the [b] following it. And that guts its resemblance to giblets and further helps it to ape gibbons. To ape Gibbon’s what? Well, as long as the Decline and Fall of the Roman Empire resembled the early declining phases of the moon, that would do.
Do you know the source and signification of this word? We see two demilunes in the bb, raising their hands as though wanting to answer our question. If you have a hunch, you’re right: it comes from Latin gibbus, meaning “hump,” and gibbous can mean “hunchbacked” in English too. But it applies more broadly to anything convex, especially if that anything is the visible part of the moon: an optimist’s moon – that is, better than half full (but not full) – is a gibbous moon, whether it be waxing or waning. (And which is which, by the way? The moon is contrary to music: when it is D for decrescendo, it is increasing, and when it is more like C for crescendo, it is decreasing.)
You won’t be surprised that moon, waxing, waning, phase, and telescope are often seen near gibbous. Oh, and also its converse – crescent, the nail-clipping-shaped moon, with a name that means “growing” though it may be decreasing and at any rate is not as big as a gibbous moon. Never mind that, though: the leaner-sounding, crisper, paradoxical crescent, perhaps more appealing as a word, too (and also displaying its referent with the c‘s), gets far more play, as its object is more iconic.