An Etymological Dictionary of the German Language/Porzellan
Porzellan, n., ‘porcelain,’ ModHG. only. “This ware, at first obtained from China and Japan, was introduced into Europe by the Italians; porcellana in Ital. orig. denoted a sea-mussel, concha veneris; since this bore a great resemblance to porcelain, the name was easily transferred from the one to the other.”