Otro (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]; Upper Aniene valley; Originally prepared by the pipers themselves, but in Anticoli Corrado (a fraction of Rome) the skin is purchased, more recently [ca. 2005], from the local butcher.
Usually made of sheepskin, rarely of goat.
Tucci, Roberta: La zampogna zoppa dell’alta valle dell’Aniene: in ricordo di Cecco Splendori. In: La zampogna: gli aerofoni a sacco in Italia (2005), I, p.92.