for: Go, Diego, Go!

Diego is a Spanish male name, derived from the Hebrew Yaʿqob (Jacob), the name of Saint James the Great, via Sant Yago, re-analysed as Santiago and SanDiego. . The assimilation of the final "T" of Sant into the name, a process called sandhi, has also occurred in "Telmo", the Spanish and Portuguese name for Elmo.

The Portuguese variant is Diogo, quite popular in the Portuguese speaking countries and comunities.

The name Diego is popular in the Spanish speaking world and also in Southern Italy (as are other Spanish names such as Fernando), due to the Spanish influence from the days of the Kingdom of Naples. For example, on the death of King Alfonso I of Naples (also known as Alfonso V of Aragon) in 1458, a famous elegy was composed by one Diego del Castillo.

The patronymic for Diego is Díaz (used for example by Rodrigo Díaz de Vivar, better known as El Cid). As with most Spanish patronymics, it has become a common Spanish surname (see Diaz for a list of people with that surname). The form Diéguez is much less common. The form Diegues is common in lusophone countries.

Simultaneous usage of several forms

During Medieval times, the names "Sant Yago", "Diago" and "Diego" seem to have coexisted.

"Sant Yago" is used, for example, in a letter by James II of Aragon dated 1300: "1 maestro de la cavalleria de Sant Yago et de la dita orden 2".

"Diago" is recorded, for example, in "Et fue a casa del Rey. e mostrolo a don diago que era adelantado del Rey" (Fuero de Burgos, ca. 1240 )

The Cid's father was named Diego Laínez. Since the Cid is believed to have been born around 1040, the name Diego can be placed in Castile at the beginning of the 11th century.

The name Didacus

Diego was translated into Latin as "Didacus" ("learned person"). Thus, for example, the usual English language name for San Diego de Alcalá (after whom San Diego, California is named) is "Didacus of Alcalá".

This form, and the simplified Spanish "Didaco", were most likely created in retrospect (that is, to translate Diego into Latin, as opposed to being the source of the name Diego). There are no mentions of Spanish people name Didacus during the Middle Ages. During those times, it was common practice to Latinize existing names, as in Ludovicus for Ludwig (Luis in Spanish).

Even so, some have insisted on deriving Diego from Didacus; nineteenth-century Spanish author Benito Pérez Galdós has a passage in his "National Episodes Series 4" (Narváez) that reads:

Su nombre es Didaco o Yago, aunque vulgarmente lo llaman Diego. (His name is Didaco or Yago, but he is commonly called Diego.)

Modern usage

In today's Spanish-speaking countries, Diego and Santiago are common as given names, while Santiago and Sandiego are found as surnames.