Once upon a time the Romans traded stuff, which they called merx. From this we get merchandise, merchant, market, mercenary and mercer. Merx also meant that the god of trade was called Mercury.
To each planet was assigned a metal: Saturn had lead, Jupiter tin, Mars iron, and Venus copper. However, the only planetary-metallic name to have survived is mercury, the stuff you find in thermometers and tuna.
Also, those born when the planet Mercury is ascendant are liable to be fast-moving and energetic and, in a word, mercurial.
P.S. To amalgamate something is to combine it with mercury. It's an old alchemical term that seems to derive from malagma in Latin, which meant bandage.