How did “gunny sack” originate?

Gunny in gunny sack is an Anglicized form of Hindu and Sanskrit goni, meaning sack or bag. Because bags for gross commodities were made on a large scale in Bengal from a strong, coarse, heavy sacking, the material itself came to be called gunny and the bags gunny sacks. The original gunny fabric was woven from the fibers of jute and hemp. Although gunny is used in India as clothing by some of the poorer classes, its chief use is in making sacks and wrappers for cotton bales and other commodities. In everyday parlance any sack of coarse material is likely to be referred to as a gunny sack.