Čep (m)
foreign object, used to repair a punctured bag of animal skin
Spherical pebble, used to repair a punctured bag of animal skin; Brest [only?]; NB: ➺ homonyms.
The pebble is forced - from the inside of the bag - into the hole; The "wart" thus caused, is wrapped up and tied firmly [on the outside?].
Širola, Božidar: Sviraljke s udarnim jezičkom [Aerophones with a beating tongue]. Zagreb, 1937, p.125.