piscine n.

early 14c., "natural or artificial reservoir for water, bathing pool," from Old French piscine "fishpond," from Latin piscina, from piscis "a fish" (from PIE root *pisk- "a fish"). The ecclesiastical sense (also piscina) "stone basin in a church placed close to the altar and used to receive the water in which the priest washed his hands before the celebration of the eucharist" is from late 15c., from Medieval Latin piscina. As an adjective from 1799.