Otre (m)
(with) definite article: il: l’air reservoir: flexible (usually of animal skin), ready for the insertion of stocks
From Latin "ǔter" [goatskin / leather bag; wineskin].
Usually made of goat-, rarely sheepskin (ewe or ram); Bags made of other material, such as rubber (caoutchouc [i.e. the inner tube of a car tyre]) don’t occur in Campania.
Gala, Giuseppe Michele: La zampogna in Campania. In: La zampogna: gli aerofoni a sacco in Italia (2005), II, p.8.