There are several and different legends about the origin of the word "Pasig". A pair of lovers, named Virgilio, a Spanish mestizo, and a Filipina beauty named Paz, customarily spent their evenings together on the bank of the river. They found a banca and went boating one moonlit night, but as fate had it, the banca capsized. Virgilio, not knowing how to swim, was carried away by the current and desperately kept afloat, but to no avail. He shouted "Paz, sigue me" (meaning "Paz, come with me"), until he could only utter "Paz sig-" and finally sank into the river. Thus the name Pasig. It was also believed that it came from the Sanskrit word "passis" or sand and refers to the community on a sandy riverbank. Historians who are less inclined to rely on a legendary romantic origin traced the town's name to the word "mabagsik" meaning violent in action or force, which aptly describes the river. Its strong and swift current brought the woods of Montalban to Manila. It was also called "mapaksik" by the Chinese living in Binondo. As time went on, "mapaksik" became "Pasik" then later on "Pasig".
Another belief was that it was derived from "pasigan" which means "baybay ng ilog", river edge or bank in English. The most convincing theory on the origin of the name came from the late Dr. Jose Villa Panganiban, a linguist, polyglot, professor and former director of the Institute of National Language. He said that the word "Pasig" is an old Sanskrit word referring to a "river flowing form one body of water to another", in the case of the Pasig River, from Laguna de Bay (pronounced Ba-l) to Manila Bay.
Total population: 505,058 (Census 2000)
Average Annual Growth Rate: 2.42 (Census 1990-2000)