A. Terminology
The Latinized Greek term baptisterium (βαπτιστήριον; baptistḗrion, from βαπτίζω; baptízō, ‘dip’) was first used by Pliny (Ep. 2,17,11) for a bathing pool; in Greek literature, however, this meaning of the word is unknown.
B. Bathing pool
In sources related to Roman baths ( Thermae [1]) the term baptisterium appears very rarely; piscina is more widely used. Such cold water pools were usually rectangular or apsidal and …