This thick, frothy drink or dessert originated in old England. It's traditionally made by beating milk with wine or ale, sugar, spices and sometimes beaten egg whites. A richer version made with cream can be used as a topping for cakes, cookies, fruit, etc. It's thought that the name of this concoction originated during Elizabethan times and is a combination of the words Sille (a French wine that was used in the mixture) and bub (Old-English slang for "bubbling drink").
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.