отличная статья с историей http://www.gear-illustration.com/2018/0 … -buttpack/
Story About USGI Buttpack
Field Pack, or buttpack, is a kind of equipment for soldiers carrying small amount of supplies, it has a long history in military use. If the supplies are too big for pockets of the clothes, and they are not enough to fill half the capacity of a backpack, buttpack is the perfect choice. This blog is about the story of GI Field Packs, or more precisely, the story about the field pack of the Vietnam War....... дальше по ссылке