Actually meaning "sock" or "socket", it can be also be a "male" term; Unfortunately I was unable to ascertain the correct gender of this part.
Sources
Web
Wikipedia (Gaita de fole), ➺ Cada secção, um termo, n°03 [NB (Oct. 2025): oddly referring to an ill. of a Scottish bagpipe!]. Dicio (➺ Definição; Classe gramatical).