dios.

Inherited from Old Spanish dios, from Latin deus (“god, deity”), from Old Latin deivos (“god, deity”), from Proto-Italic *deiwos (“god, deity”), from Proto-Indo-European *deywós (“god, deity”), from *dyew- (“sky, heaven”). The form in -os continues the Latin nominative, not the expected accusative as in Ladino dio. This may be due to Ecclesiastical Latin influence. Compare the name Marcos alongside Marco, the former of which may have been spread via the name of the gospel author (though Carlos is not a biblical name and also appears in the nominative form). Obvious examples of this are Isaías, Jesús, Moisés, and Mesías (“Messiah”). On the other hand, the phenomenon can also be explained as a native Vulgar Latin development: Words like “God” and personal names often appear in the vocative, for which Vulgar Latin used the nominative form, and this form may then have been generalized when case distinction was lost. This parallels instances in Old French and Old Occitan where the word for “God” appears in the nominative form regardless of its syntactic function. (See also Middle French Dieux alongside Dieu.)