Siren is another contranym, now I come to think about it: it can mean a sound that warns you to get out of the way, or one that lures you closer.
The luring-closer sirens were originally sea nymphs whose singing lured sailors onto the rocks.
This picture is by John William Water House, but of course no one's sure what sirens really look like. Apart from anything else, they're unlikely to exist. Here's another version:
The guy tied to the mast in this picture is Odysseus. The other people all have their ears stopped up with wax to stop themselves being lured onto the rocks.
The story of Odysseus and the sirens is ancient Greek, but there are still sirens about: any attractive woman can be called a sirens if she's using her beauty to exert power over people.
This modern sort of siren definitely exists.
Also definitely existing is the last sort of siren. You find these in North and parts of Central America, but only if you're prepared to look in damp places.
This is the Greater Siren, Siren lacertina. It's probably a sort of salamander, but it lacks hind legs and eyelids, and it has a horny beak. It can grow to nearly a metre in length and it eats slugs and snails (oh, I wish I had one in my garden) and sometimes fish. If there's a drought then they make themselves a burrow and then make themselves a water-tight coating with stuff that oozes out of them.
A habit, I would think, unlikely to lure anyone anywhere.
Word To Use Today: siren. This word arrived in English in the 1300s from France. The Old French word was sereine, from the Latin sīrēn, from the Greek seirēn.