As stated in the traditional grog recipe post, the term “grog” originally referred to a diluted rum drink that was given to British sailors to prevent scurvy in the 1700s. It is said that the drink was named after Admiral Edward Vernon, who was nicknamed “Old Grog” because he wore a grogram coat. When he ordered the dilution of the sailors’ rum rations with water, the drink became known as “grog” in his honor.
The only real difference between the traditional and the navy is the fact that the navy grog has a splash of grapefruit juice.