The much fabled Arroyo wealth is attributed to First Gentleman (FG) Juan Miguel “Mike Tuason Arroyo”, a direct descendant of Chinese Businessman Son Tua who was gifted with a vast tract of land as encomienda by the Spanish rulers. As the FG narrated in a senate testimony, Son Tua was made to ride a horse from sunrise to sunset and was given ownership of the land that he covered (Sta Mesa, Diliman & Marikina). Later on, he bought Marikina at a public auction.
Son Tua, I can only surmise, changed his name to Tuason, hence the Tuason in FG’s middle name. The changing of names during the Spanish era was a result of religious conversion and later on, a law mandating the changing of Filipino names to Hispanic based on a book of approved names – Catalogo de Alfabetico de Apellidos.