Epsom salts
Concise Oxford English Dictionary © 2008 Oxford University Press:
Epsom salts/epsəmˈsɔːlts/
▶plural noun crystals of hydrated magnesium sulphate used as a purgative.
– origin C18: named after the town of Epsom in Surrey, where the salts were first found occurring naturally.
'Epsom salts' also found in these Oxford entries:

