Swiss Miss is a brand of instant hot chocolate that is manufactured by ConAgra Foods. It was first introduced in the 1950's, under the name Brown Swiss, and was marketed only to airlines. When it became obvious that there was a consumer market for instant cocoa, the name was changed to Swiss Miss and it began to be sold in supermarkets.
Swiss Miss can be recognized by a picture of a blonde girl on the package. I assume that she is the "Swiss Miss". In addition to regular and sugar-free hot cocoas, both with and without marshmallows, Swiss Miss also makes pudding snack packs and instant apple cider.