Apparently from Finnish "pilli" [whistle]; NB: The Russian website proved to be the only source in which this term is mentioned; Even though it shows an illustration, in the caption of which it refers to М.Гютри, «Diesertations [sic] ...» [i.e. Matthew (Mathieu) Guthrie, »Dissertations sur les antiquités de Russie« (Saint-Petersbourg, 1795)], my close scrutiny of the entire text of that source remained fruitless (➺ Internet sources) ...; NB: ➺ Pilai.