Méndez ranks 26th in Ourense Province with 22,588 occurrences across 252 municipalities. A patronymic from "Mendo" or "Menendo" — derived from the Germanic Hermenegild, meaning "complete sacrifice" — the surname was particularly common in medieval Galicia and northern Portugal, regions where the given name Mendo was favored by the lesser nobility and landed gentry.

Unlike the more evenly distributed surnames in the Ribeiro region, Méndez shows a distinctly concentrated pattern. Its strongest presence is in Castrelo de Miño (99 bearers, 2.42%), with smaller numbers in Cartelle (36, 0.50%) and Arnoia (11, 0.45%). The surname is notably absent from the Ribadavia, Cenlle, Beade, and Leiro municipal censuses, suggesting a very localized origin tied to specific parish communities.

In the Inquisition records, Méndez shows a significant 6.9% frequency in Ribadavia trials, despite being absent from the Ribadavia municipal census. This paradox suggests that Méndez families in the medieval Jewish quarter may have relocated to nearby Castrelo de Miño or other parishes after the 1492 expulsion, maintaining the surname in a more rural setting.