This is actually the essence of the meaning. From the way of word formation, stick ice, is the ice in the shape of a stick; popsicle, is the ice made into a stick shape. But there is a certain difference, "popsicle" refers to the traditional "old popsicle", which only added sugar, simple flavor; and "stick ice" is a modern craft products, added with the inclusion of Food coloring and other flavorings, including additives, taste better.