Warning: the following was typed 10 hours after surgery while under the influence of pain medication. Please disregard grammatical and spelling errors, and understand that it may not make any sense at all. Or maybe it makes perfect sense.
There's no real point in spoilering adamantine itself. Slade too. The game has the fact that these minerals exists plastered all over it. It's in your stockpile lists, the Manager's job screen, I've had dwarves with a particular fetish for raw adamantine plenty of times. So the fact that adamantine exists, no point in spoilering. Definitely
no point in euphemisms.
In fact, the euphemisms are what is spoiling the surprise, as Anathema said, because you know for sure something
is there. And since people tend to be very specific about the scenario when using the euphemisms, so new players know exactly what's going to happen
. They just don't know the real name of the beast that will do them in.
If you want to talk about spoiler material without spoiling it for new players, we have spoiler tags
Because cottoncandy/circus/clowns is just a useless, bad meme. And that's why we'll never fully be able to get rid of it, because like every useless bad meme in any internet community, the newer members will perpetuate it, in an effort to demonstrate that they belong