There are many conjectures as to the origin of the name Pasay.
In one version, the name of the municipality came from the wail of a brokenhearted swain. Jose and Paz were in love with each other and were intent on a life together, but Jose's father was a mere tenant of the hacienda of Paz's father. For this reason, their love was forbidden and Jose was ordered to stay away from Paz. Unable to bear her misfortune, Paz died.
At her funeral, the elite came to mourn and pray as Jose watched from a distance. As soon as everyone left, Jose dug a tunnel into the earth to be with Paz. Once joined, he let out a sharp and anguished cry "Paz-ay!" In sorrow and regret, the parents of Paz named their hacienda Paz-ay. In time, the town came to be known simply as Pasay.
Historians have another explanation for the origin of the name of the city. It is said that back in the day, Pasay was thick with pasaw, a plant with an exotic aroma. It was said that a Spanish botanist, Antonio Pineda, frequented a place called Basal in the vicinity of San Rafael to gather pasaw.
Pasay may also have come from the name of an ethnic group called Pasai in Malaysia.
The version deemed to be most credible is that Pasay was named after a princess of the Namayan Kingdom, Dayang-dayang Pasay. The Namayan Kingdom was a confederation of barangays that began to peak in 1175 and extended from Manila Bay to Laguna de Bay. Dayang-dayang Pasay inherited the lands now comprising the territories of Culi-culi, Pasay and Baclaran. The royal capital of the kingdom was built in Sapa, known today as Santa Ana.
The natives brought their products to the capital of Namayan. Trading flourished during the 12th to the 14th centuries. Merchants from China, Moluccas, Java, Borneo, Sumatra, India, Siam, and Cambodia came to trade with the natives.
Pasay's name may also have originated from the Spanish Paso hay meaning there is a pass. This referred to the paths cleared among the grass leading to the southern portions from Manila.