When you look at certain kinds of birds in the right light, their feathers can seem to change color in the light. In much the same way, silk and some other fabrics don’t always look quite the same as changing light hits them; you can see different colors and even patterns appear.
This is caused by the reflections and refractions of light as it hits tiny fibers and filaments. Another instance where you see a similar effect is in a cut gemstone as it moves in light — or light moves across it. There are even some varieties of automobile paint that shift colors depending on the angle of your view.
This effect has fascinated people for centuries, and as you might expect, there have been a number of words for it. In the early 1600s you would have said that bird’s feathers were “cangeant” or “volant.” “Cangeant” came from “change” and applied to anything, but “volant” might have applied only to birds and their feathers, because it comes from the Latin “volare,” which means to fly. Another bird-related adjective that was used was “pavovine” — that one meant “like a peacock.”
In the 1700s the same quality was termed “versicolored,” “perlaceous” (like a pearl), and finally a word that stuck: “iridescent.” That last one is based on rainbows; it comes from the Greek goddess Iris, who appeared as a rainbow. Even though “iridescent” showed up around 1794, though, “pavonated” (peacocks again) reappeared in 1798, and “chatoyant” was used around 1816.
“Chatoyant” is an outlier in the set of words referring to shimmering colors; it has nothing at all to do with birds or rainbows or even pearls. Instead, it’s about cats. It’s based on the way cats’ eyes shine in the dark. It’s borrowed from French — “chat” is French for cat, and the rest is the same as the ending of “flamboyant.”
Even though plenty of words were already available to describe this effect, more kept getting added after 1800. There were some new ones based on pearls (“nacreous,” “nacrous,” “nacry,” and “nacrine”), a couple based on rainbows (“iridine” and “irisated”), and finally, possibly because of new discoveries of opals, which I think were pretty rare at one time, “opalescent.”
Then there’s the word used in the mid-1800s that wins prizes both for simplicity and for seemingly lacking any allusion to anything the effect resembles: “shot.” Thomas Huxley, in his 1877 “Manual of the anatomy of invertibrated animals,” explained: “The peculiar play of ‘shot’ colours, which pass like blushes over their [sc. Cephalopoda] surface, in the living state.” Yeah, sure. But we know what he really meant. Chatoyant.
