Word Originmid 17th century (in the form nollaes, plural, perhaps after Portuguese): from Bengali nālā and Hindi nālā, from Sanskrit nāla ‘hollow stalk, tube’.
A nullah or nala is an 'arm of the sea', stream, or watercourse, a steep narrow valley. Like the wadi of the Arabs, the nullah is characteristic of mountainous or hilly country where there is little rainfall. Wikipedia
