Derived from Ancient Greek κοραλλιον (korallion) meaning "coral" (in Modern Greek κοραλλι). This was the name of an obscure 4th-century saint and martyr from Thrace.
From the English and Spanish word coral for the underwater skeletal deposits which can form reefs. It is ultimately derived (via Old French and Latin) from Greek κοραλλιον (korallion).