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 Aquae Spadanae, sometimes incorrectly connected to the Latin word spargere meaning to scatter, sprinkle or moisten.
Since medieval times, illnesses caused by iron deficiency 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 Walloon word for “fountain”).