A gunny sack, also known as a "gunny shoe", is an inexpensive bag made of hessian usually formed from jute or other natural fibers, although modern sacks are often made from polypropylene; the "gunny" portion of the name ultimately descends from Sanskrit guṇa, "thread, fiber", by way of imperial British corruption of that word's descendants in later Indian languages. Gunny sacks are traditionally used for transporting grains, potatoes, and other agricultural products. Today they are also sometimes used as sandbags for erosion control. Gunny sacks are also popular in the traditional children's game of sack racing.
A gunny sack holds approximately 100 lb (45 kg) of potatoes. Even though gunny sacks are no longer used for that purpose, among Idaho farmers the common measurement unit of potatoes is still the "sack".
Because gunny sacks are/were (traditionally) made from natural fibers, they are considered to be environmentally friendly. High breathability allows air to pass through them, which helps packaged grains or other agricultural commodities to stay fresh.
Sacks made from jute, hemp, and kenaf fiber have high tensile strength. As a result, piling sacks one on top of the other does not tear or distort the yarn of the lowest residing sacks in the pile.