In the lives of ordinary people there is a tendency to use different words which meanings are not known to everyone. This list may include a fashionable nowadays word “SPA”.
There are two versions of the origin of the term. According to one version ancient Romans called with this word thermal springs with the help of which they treated various ailments and simply relaxed the body after endless wars and conquests. Even then people understood that a man can not live without natural water resources.
Another version says that the term is derived from the name of a very famous resort in the world. You can compare it with the words "xerox" or "foam", which are also brand names that are very firmly established in the vocabulary of a person.
However the origin of the word makes little difference. It was SPA and it has remained SPA. It is not worth thinking what this word means. One should better go and feel all charms of SPA procedures.
Then there should come understanding of ancient Romans and those people who had a rest at the same resort of thermal waters. A man is a very suspicious person especially in our time. So it is better to see once and feel than to hear from someone a hundred times.