Díaz is a common surname of Spanish origin with multiple meanings in multiple languages. First found in the Kingdom of Castile, where the name originated in the Visigoth period, the name accounts for about 0.17% of the Spanish population, ranking as the 14th-most frequently found surname in both 1999 and 2004. Variants and related names. There is minor evidence that Díez may be equivalent to Díaz, in the form of Spanish language listing of most frequent surnames in 1999 Spain.
https://en.wikipedia.org/wiki/D%C3%ADaz_(surname)