San Agustin is popularly known as Dapa, meaning to lay down flat on the ground. This was the order of the lieutenant of the revolutionary forces to his soldiers.

The barrio has three sitios Payapa, Balibago and Balas. Payapa is meant peaceful because the soldiers who retreated in that sitio were not molested and stayed peacefully. Balibago is the place where there are plenty of Balibago trees. Balas is meant sandy. This was the result when the banks of the Dapa Creek overflowed and left the place sandy.