Come across this recently, probably just an old idea resurfacing as these things seem to do. Thought it worth mentioning so you can kill it if you come across it !
Spa (health resort, water jet bath etc.) is from the town of Spa in Belgium (so far OK). The town gets it name from the Latin phrase “Sanitas Per Aquam” (SPA) meaning “health through water”. This second part is false; like most acronyms this one is a recent invention (backronym).
Where the town gets its name from is not too clear. One suggestion is from a Walloon word for spring, “espa”. But this might have actually come from the town name as well! So it might be from the latin “spagere”, sprinkle or moisten. English word sparge is not suprisingly from the same root (via french).