 Because Pedro de Medina derived his surname from the Andalusian city of Medina-Sidonia, the name Medina comes from the Arabic for city.The Texas Legislature formed Medina county on February 12, 1848 and enlarged it on February 1, 1850 using land taken from Bexar County.Castroville was the county seat, and the county erected the first permanent courthouse there in 1854.