A Spa is a location where mineral-rich spring  water....

The term is derived from the name of the town of Spa, Belgium, whose name is known back from Roman times, when the location was called Aqua Spadanae, sometimes incorreclty connected to the Latin word spargere meaning to scatter, sprinkle or moisten.

Since medieval times, illness caused by iron defiency were treated by drinking chalybeate (iron-bearing) spring water (in 1326, the iron-master Collin le Loup claimed a cure, when the spring was called Espa, a wallon word for "fountain".