E. De Felice, A. Bongioanni and F. De Laurentiis agree that the surname Giordano derives from the personal name Giordano, one of the most widespread biblical names in medieval Italy. The name is documented as early as the 2nd and 3rd centuries in Christian Latin inscriptions under the form Iordanus, derived from the Greek Iordanés and ultimately from the Hebrew Yardén, the name of the Jordan River.

The popularity of the name is closely connected with Christian tradition, since the Jordan River is the place where Jesus was baptized. This religious significance favored its widespread use as a given name throughout the Middle Ages and later led to its establishment as a hereditary surname. As a result, Giordano became one of the most common surnames in Italy.

F. De Laurentiis notes that the Hebrew name Yarden is probably related to the root yarad (“to flow” or “to descend”), while some interpretations associate it with the meaning “river of two branches.” He also considers surnames such as Giordani to be direct variants of Giordano, sharing the same origin.

A. Bongioanni adds that the cult of Saint Jordan, celebrated on 13 February, further contributed to the diffusion of the name. He also mentions that in certain Germanic contexts the name was associated with the Gothic form Iornandes, suggesting later cultural adaptations beyond its original biblical meaning.

Several regional variants developed from the same root, including Giordani, Giordan, Giordana, Giordanelli, Giordanetto, Giordanengo, Giordanino and Giordaniello. The Venetian surname Zordan is considered a dialectal form of the same name. Together, these variants reflect the extraordinary diffusion and local adaptation of one of Italy’s oldest and most enduring biblical surnames.