An Etymological Dictionary of the German Language/Annotated/Schelle
Schelle, feminine, ‘small bell,’ from the equivalent Middle High German schëlle, Old High German schëlla, feminine; allied to Middle High German schëllen, Old High German scëllan, ‘to sound loudly, resound,’ to which Italian squilla, ‘little bell,’ is also akin. — Modern High German and Middle High German schellen, literally ‘to cause to resound,’ is the factitive form. Compare verschollen, ‘vanished,’ as a relic of the Middle High German strong verb.