Often, Epsom salts. Chemistry, Pharmacology. hydrated magnesium sulfate, MgSO 4 ⋅7H 2 O, occurring as small colorless crystals: used in fertilizers, the dyeing of fabrics, leather tanning, etc., and in medicine chiefly as a cathartic.
1760-70; after Epsom; so called from its presence in the local mineral water
1770, obtained from Epsom water, the water of a mineral spring at Epsom in Surrey, England. The place name is recorded c.973 as Ebbesham, lit. "Ebbi's homestead," from the name of some forgotten Anglo-Saxon.