Magnesium sits at the centre of one of chemistry's tangled etymologies. The place-name Magnesia gave rise to three distinct words: magnet, from the lodestone said to be found there; manganese, from a black ore; and magnesium, from the white earth magnesia alba, long used medicinally as a laxative and antacid (milk of magnesia, Epsom salts). The element has no planetary or alchemical role of its own, being isolated only in the nineteenth century, but the mineral magnesia alba was a familiar apothecary's substance well before Davy's battery separated the metal within it. Magnesium's brilliant white flame later made it the light of early flash photography.
Epsom salts take their own name from the town of Epsom in Surrey, where a bitter mineral spring was discovered in the early seventeenth century and swiftly became a fashionable spa cure, its purgative and, later, supposed muscle-soothing properties promoted well beyond what evidence supports; magnesium sulfate baths remain a folk remedy today though the sulfate ion barely crosses the skin. Milk of magnesia, magnesium hydroxide suspended in water, is a still-familiar over-the-counter antacid and laxative, so that two of magnesium's oldest medicinal names, one a spa town and one a description of appearance, both survive in the modern pharmacy.