Atlantis
the sunken civilization
Today this word meansThe legendary civilization drowned by the sea. Figuratively, anything vanished without a trace.
The island nation Plato set down in his Timaeus and Critias.
The name means "(island) of Atlas," from the same root as Atlantic.
After the American writer Donnelly popularized the claim that it was real in the nineteenth century, hundreds of sites have been nominated as candidates.
Worth noting
Not one record mentions Atlantis before Plato. The scholarly consensus treats it as his invention, not inherited myth.