The Spanish word 'piscina' (meaning 'swimming pool') comes from the Latin word 'piscina' which meant 'fish pond'. The Latin 'piscina' itself was derived from 'piscis' meaning 'fish'. This etymology shows how the meaning evolved from a pond specifically for fish to a general pool for swimming. This semantic shift reflects how the primary purpose of artificial water containment shifted from fish-keeping to human recreation over time.

A related Spanish word is 'pez' (fish), which also comes from the Latin 'piscis'. While 'piscina' retained its connection to contained bodies of water, 'pez' maintained the direct meaning of 'fish' from the original Latin root.

English speakers might recognize this connection in words like 'piscine' (relating to fish) and 'pisces' (the astrological sign of the fish), both of which come from the same Latin root 'piscis'. The word 'fish' itself, however, comes from a different Germanic root.