Dreibrünchen (n)
(with) definite article: dasProbably a late 18th/early 19th century corruption, or an incorrect spelling by Foxo.
Foxo, Xosé Lois: Estudio lexicolóxico da cornamusa. In: Anuario da Gaita 1995 (10), p.51 (»Hienze [sic] [Ms. 1799-1803]).