An Etymological Dictionary of the German Language/Annotated/Stöpfel
Stöpfel, Stöpsel, masculine, ‘stopper, cork,’ a Modern High German derivative of stopfen, verb, ‘to stuff, cram, mend,’ Middle High German stopfen, Old High German *stopfôn, of which a variant stoppôn, weak verb, ‘to stuff,’ occurs; to the latter, Dutch stoppen, Anglo-Saxon forstoppian, English to stop, correspond. The assumption that the word was borrowed from Middle Latin stuppare, ‘to stop with tow’ (from Latin stuppa, ‘tow’; compare Italian stoppare, French étoupper), is open to objection. It is more closely related to Middle High German stupfen, stüpfen, Old High German stopfôn, ‘to pierce.’ With the implied Aryan root stup (tup) is connected Sanscrit stump (tump), ‘to push, thrust’ (Greek τύπτω?).