Edward Vernon was worried, so worried that he decided to take drastic measures. His men were simply drinking too much, the rum was disappearing down their throats. And he dictated the order, as Admiral that he was, that the rum had to be watered down a lot. There was no choice, so the sailors had to water down the rum and that was not the same, so they tried to improve it by adding lemon or cloves or other spices.
Vernon always wore his cloak made of a mixture of wool and silk; a fabric called grogram. Hence the Admiral was known as Old Grog, from which the name of the new brew was derived: grog. And no matter how diluted the rum was, the effects of the alcohol were also noticeable, so that those affected were said to be 'groggy', a term that is still used today.
We have seen grog associated with the typical drink of pirates and it is also referenced in Hollywood, in films such as Master and Commander or even in the Hobbit and also in a few video games.
But we should not confuse rum with water and 'stuff' with wine without water and 'stuff' even though the names of both drinks are similar: grog and glögg.
Glögg is the Swedish version of what would be "Forralt bor" in Hungarian, "vino quente" in Portuguese or - perhaps the most popular - Glühwein in German. It is basically mulled wine with its additives. It is prepared with wine -usually red wine, with some exceptions such as Austria- which does not have to be the best reserve wine, nor does it have to be an average wine, but it must be good, decent. It is prepared by cooking lemon and orange peel with sugar and then spices and aromas such as cinnamon, cloves, star anise, cardamom, bay leaf, a pinch of nutmeg... the complements vary. The essential thing is that it must not boil when the wine is added. In 30 minutes, it is ready, just add the sugar to taste and strain the result through a sieve. In Scandinavian countries they add vodka, of course.
Evolving and positioning itself also as a typical Advent drink. From the "vino navegado" or "candola" wine that is drunk in Chile in winter to the aforementioned glögg that is drunk for Saint Lucy on 13 December to the glühwein that you will find at all the Christmas markets in Central Europe, such as those in Prague or Munich. A warm experience.