Knapsack

A backpack — also called bookbag, kitbag, knapsack, rucksack, pack, or sackpack — is, in its simplest form, a cloth carried on one's back and secured with two straps that go over the shoulders, but there can be variations. Lightweight types of backpacks are sometimes worn on only one shoulder strap.

Backpacks are commonly used by hikers and students, and are often preferred to handbags for carrying heavy loads or carrying any sort of equipment, because of the limited capacity to carry heavy weights for long periods of time in the hands.

Large backpacks, used to carry loads over 10 kilograms (22 lb), as well as smaller sports backpacks (e.g. running, cycling, hiking and hydration), usually offload the largest part (up to about 90%) of their weight onto padded hip belts, leaving the shoulder straps mainly for stabilising the load. This improves the potential to carry heavy loads, as the hips are stronger than the shoulders, and also increases agility and balance, since the load rides nearer the wearer's own center of mass.

In ancient times, the backpack was used as a means to carry the hunter's larger game and other types of prey and as a way of easier transport for other materials. In the cases of larger hunts, the hunters would dismember their prey and distribute the pieces of the animal around, each one packing the meat into many wrappings and then into bags which they placed on to their backs. The bag itself would be made up of animal hide and skin and sewn together by animal intestines, which would be woven together tightly to make a sturdy thread-like material.

The word backpack was coined in the United States in the 1910s. Moneybag and packsack were used prior, and now occur mainly as regionalisms.

The word rucksack is a German loanword mainly used in the UK and in Western military forces. In German, Rücken means "back" and Sack means "bag". The name rucksack is cognate with the Danish rygsæk, Norwegian ryggsekk, Dutch rugzak, Afrikaans rugsak and Swedish ryggsäck.

The word knapsack was the usual name for a rucksack or backpack up until the middle of the 20th century.

Alternative names include haversack (which more properly describes a small cloth bag on a strap worn over one shoulder to carry havercakes or oatcakes), Kraxe (a German rucksack with a rigid framework), and bergen (a large load-carrying rucksack, from a design issued by the British Army during the Second World War). In fact, Britons used to call Alpine-style backpacks "Bergen rucksacks", maybe from the name of their creator, Norwegian Ole F. Bergan, combined with the name of the Norwegian city of Bergen.

...
Wikipedia