 Perai, situated at the estuary of the Perai River, lent its name from the waterway.Upon the acquisition of the area by the British East India Company in 1800, the river was known in Thai as "plai" (), which meant ""the end"", as it formed the border between British "Province Wellesley" and the Siamese vassal state of Kedah; the Perai River thus marked the southernmost limit of Siamese influence.British maps of the era referred to the southern banks of the Perai River as "Prye".