This word appears to have come into northern use via Eskimopoq, puqbag; perhaps borrowed from early whalers in this sense.
1931  Formerly the Eskimos killed walruses with spears. The spear would not kill them outright, of course, but attached to it was a long sealskin line at the end of which was fastened an inflated sealskin bag called a pok.
2n. a sealskin bag used by Eskimos for storing or transporting seal or whale oil.