This is one of those things that I’ve long wondered about, but never managed to check out. A piece — apparently aimed at kids — in the Christian Science Monitor yaks about assorted origins of the names of elements and their symbols. Inter alia, the symbol for mercury is glossed thusly:
But my favorite symbol is the one for the only metallic element that is a liquid at room temperature – mercury, symbol Hg. I have a small vial of mercury that I swirl around for my students. The ancient Romans regarded mercury as a type of silver that flowed. They therefore called it “liquid silver” or hydragyrum, hence its symbol.
I suppose we can call that Latin (from the ending), but surely it must go back to Greek hydr- (liquid/water) and argyros (silver). And, of course, the word must be hydrargyrum, unless it underwent some sort of further change …
