Which element was named for a village in Sweden that also gave its name to three others?

Yttrium, from Ytterby - a village on an island near Stockholm whose feldspar quarry produced a single black mineral that turned out to contain a crowd of new elements. Four are named directly after it: yttrium, terbium, erbium and ytterbium.

Three more came out of the same rock and are named for the region or its discoverers - scandium, thulium and holmium - so one small quarry accounts for seven entries in the periodic table, more than any other place on Earth.

Untangling them took a century, because the rare earths are chemically almost identical. Their outer electrons are the same and the differences hide in an inner shell, so they behave alike in every separation anyone could devise, and chemists repeatedly announced an element that was later shown to be two or three. The industrial method that finally worked, ion-exchange chromatography, came out of the Manhattan Project. They are not rare, incidentally - cerium is more common than copper - only awkward to separate, which is why supply is concentrated and politically fraught.