False friend
A genus named for looking like something else, and a poison named after a folk remedy.
There is a genus of diatoms whose name means, more or less, the false version of the other one.
Pseudo-nitzschia. The second half is Nitzschia, a genus named in the usual nineteenth-century manner after a man - Christian Ludwig Nitzsch, a German naturalist who worked mostly on birds and their parasites and, as far as I can tell, had no particular involvement with algae. The first half is pseudo-, false. So the full name unpacks to: the thing that resembles the group named after the man who studied something else.
Once you start noticing this you find the naming system is riddled with it. Pseudo-, para-, quasi-, and the suffixes that do the same work quietly - -oides and -opsis, both meaning “looking like”. Whole branches of the tree of life are labelled not with what an organism is but with what somebody initially took it for. Taxonomy is supposed to be a record of relationships. A surprising amount of it is a record of our own confusion, preserved in Latin.
I have some affection for this. It’s an honest sort of failure to have written down.
The thing Pseudo-nitzschia is best known for is a molecule called domoic acid, and that name has a much stranger history than the organism’s.
It doesn’t come from Greek or Latin. It comes from domoi, a local name on one of the Japanese islands for a particular red seaweed. The seaweed was used as a traditional remedy, given to children to expel intestinal worms - which it apparently did rather well, because the compound is neurologically active and a worm is a nervous system with a body attached. When chemists eventually isolated the active substance in the mid-twentieth century, they named it after the plant they’d pulled it out of, which had been named by people who had no idea what was in it and simply knew it worked.
So the word is a place-name for a cure.
Then, decades later, it turned up somewhere else entirely.
In 1987 a large number of people on Prince Edward Island became seriously ill after eating cultivated mussels. The symptoms were disorienting - vomiting and cramps, which you might expect, and then confusion, seizures, and in some cases a permanent loss of the ability to form new memories. Several people died. It took a scramble of a few weeks to work out that the mussels had been filtering a bloom of Pseudo-nitzschia out of the water and concentrating the same compound in their tissue.
The illness got the name amnesic shellfish poisoning, which has to be one of the bleaker diagnostic terms in medicine.
It is also, I think, the reason to bother with etymology at all. On the label of a shellfish harvesting closure, domoic acid is a piece of regulatory vocabulary and nothing else. Underneath it is a small island, a seaweed, and somebody’s grandmother giving a child something for worms. The word carries the remedy inside the poison and doesn’t mention which is which.
There’s a footnote to this that I’ve deliberately left until the end, because it’s the sort of thing that gets repeated more confidently than it deserves.
In 1961, in a town on the Californian coast, large numbers of seabirds behaved very oddly - flying into buildings, coming down in the streets, dying in numbers. It was reported in the local paper. Alfred Hitchcock, who was working on The Birds at the time, is said to have asked for the clippings.
Much later, someone went back to plankton samples archived from that stretch of coast and found the organisms and the conditions you’d expect if domoic acid had been moving up the food chain. It’s a good explanation and it fits. It is not the same thing as a measurement taken at the time, and the birds are not available for comment. I’d file it under probable rather than known, and I notice that I want it to be true, which is exactly when to be careful.
One last thing, which is either a coincidence or the universe showing off.
In linguistics, a false friend is a word that looks like it means the obvious thing in another language and doesn’t. Embarazada is not embarrassed. Actuellement is not actually. And the example that appears in every first lesson on the subject is the German Gift, which does not mean a present. It means poison.
The route there is grim and completely logical. Gift and give are the same word. A gift is a thing given. A dose is also a thing given, and at some point the word for the administered dose narrowed to the word for the harmful one, and the pleasant meaning fell away entirely in German while surviving intact in English. The two languages kept opposite halves of the same idea.
So: a genus named false, a toxin named after a cure, and the textbook example of a false friend turning out to mean poison.
Names remember what somebody noticed first. Occasionally they also remember what somebody hoped.