Glühwein is red wine heated with spices, typically consumed in the winter festive season in German speaking countries. While the preparation resembles that of anglophone mulled wine, the spices may be different, and savvy marketers have begun selling products in the UK which say on the label Glühwein, probably playing on the popularity and reputation of German Christmas markets. If the German term seems more concise and attractive to anglophones than mulled wine, it could well be adopted by the English language.
Gluhwein may have been invented to dispose of inferior and otherwise unpalatable wine, and was originally heated with a glowing iron rod. When it cools the drink does not taste as good and so encourages prompt consumption and merriment.