The pipebag is the air supply of the bagpipe
it is held under the arm and squeezed to provide wind to the drones
Historically pipebags have been made from animal hides, the ideal being a hide from an animal native to the area the pipe is being played, for example, elkhide in Canada, and Kangaroo hide in Australia. This is because the bag must keep the air in and let the moisture out
animals native to a habitat naturally have the best skins suited to this task.