waterbag

noun2

1. •
   A bag for carrying water.

   • Who'll come a'waltzing Matilda my darling Who'll come a'waltzing Matilda with me Waltzing Matilda and leading a water-bag Who'll come a'waltzing Matilda with me. — 1895
2. •
   (historical) The bag-like compartment in a camel's hump in which the animal was once believed to store water; in fact it is fatty tissue.