Otre (m) (plurale tantum?)
plural: = singular; (with) definite article: gl’air reservoir: flexible (usually of animal skin), ready for the insertion of stocks
From Latin "ǔter" [goatskin / leather bag; wineskin]; Central Latium.
Ricci, Antonello: Musicisti e zampogne del Lazio meridionale. In: La zampogna: gli aerofoni a sacco in Italia (2005), I, p.134.