An Etymological Dictionary of the German Language/Stöpfel
Stöpfel, Stöpsel, m., ‘stopper, cork,’ a ModHG. derivative of stopfen, vb., ‘to stuff, cram, mend,’ MidHG. stopfen, OHG. *stopfôn, of which a variant stoppôn, wk. vb., ‘to stuff,’ occurs; to the latter, Du. stoppen, AS. forstoppian, E. to stop, correspond. The assumption that the word was borrowed from MidLat. stuppare, ‘to stop with tow’ (from Lat. stuppa, ‘tow’; comp. Ital. stoppare, Fr. étoupper), is open to objection. It is more closely related to MidHG. stupfen, stüpfen, OHG. stopfôn, ‘to pierce.’ With the implied Aryan root stup (tup) is connected Sans. stump (tump), ‘to push, thrust’ (Gr. τύπτω?).