Castaldi is an occupational surname derived from the medieval terms castaldo and gastaldo, which in turn come from the Lombard word gastaldus. According to E. De Felice and E. Rossoni, the term originally designated an official responsible for administering royal property and exercising civil, military, and judicial authority on behalf of the ruler.

Over time, the role evolved and came to refer more generally to the administrator of estates, agricultural properties, or institutional lands. The surname therefore originated as a nickname identifying a person who held such an office or performed similar administrative duties.

Distribution

According to Rossoni, Castaldi is found throughout Italy, with significant concentrations in the areas of Varese, Ferrara, Firenze, Lazio, and Campania.

De Felice notes that surnames beginning with Ca-, such as Castaldi, are especially characteristic of central and southern Italy and are particularly frequent in the area of Napoli, although they are also present in Toscana, Emilia-Romagna, and Lombardia.

Variants and Related Surnames

• Castaldo is one of the principal surnames derived from the same medieval office.
• Gastaldi and other forms beginning with Ga- reflect a closer preservation of the original Lombard term and are more common in northern Italy, especially in Piemonte and Liguria.
• Castoldi, according to Rossoni, is a related surname that originated in the province of Pavia.

Notes

De Felice explains that the office of gastaldus underwent several historical transformations. During the Lombard period, the gastald administered the royal curtis; later, the office was extended to the estates of dukes, counts, and ecclesiastical institutions. Under Frankish rule, the title continued as a state office before eventually becoming associated with the management of agricultural and private properties.

An early example of the term used as a personal name appears in Lucca in the year 774, where a Castaldus clericus is recorded in the Codice diplomatico longobardo.

The surname preserves the memory of one of the most important administrative offices of medieval Italy and reflects the influence of Lombard institutions on the development of Italian family names.