Trịnh–Nguyễn War
Beginning in the 1620s, Prey Nôkôr was gradually settled by Vietnamese refugees fleeing the Trịnh–Nguyễn War further to the north. In 1623, Khmer king Chey Chettha II (1618–1628) allowed the Vietnamese to settle in the area, which they colloquially referred to as "Sài Gòn", and to set up a custom house at Prey Nôkôr. The increasing waves of Vietnamese settlers which followed overwhelmed the Khmer kingdom—weakened as it was due to war with Thailand—and slowly Vietnamized the area. Upon capturing the city during the Cochinchina Campaign in 1859, the French officially westernized the city's traditional name into "Saigon" ().