Possibly related to the noun пулчелык [pulče•lə̑k; knottiness, knagginess (wood)] and the adjective пулче [pulče•; knotty, knaggy (wood)].
Sources
Web
Mari Research Institute (Технология изготовления шўвыр (волынки) [Manufacturing technology of the Šŭvyr (bagpipe)]; NB: in Russian only) Mari dictionary (➺ Cyrillic / All matches; челык [NB: ➺ ref. to "PARENT" пулче•])