Where the Castro name comes from

Castro comes out of Galician and Portuguese, from the Latin castrum, meaning a castle or fortress. In Galician it began as a habitational surname, taken from a place and carried by the people who came from it. Portuguese inherited it from Old Galician-Portuguese Castro, from castro, a fortification, and used the word as a toponym marking the presence of a fort. Portuguese also kept an alternative form of the name, Crasto.

The Spanish surname runs back by a separate line, probably ultimately to the Latin castra, a military camp. Its English equivalent is Chester. From Spanish it reached Pangasinan, introduced there through the Catalogo alfabetico de apellidos.