The name Boac is derived from the Visayan word biak, which means "divided". The town had been divided into by a river running from the eastern hinterland to the western plains down to the sea. The two were the Northern and the Southern areas.
Other records says that Boac came from the word "bulwak", which characterizes the tide caused by the rapids of the Boac River to its mouth in Brgy. Lupac and to the banks around the riverside barrios.