Grog is an alcoholic beverage made by mixing rum with water. It is a popular drink in many parts of the world, and has been around since the 18th century. The term 'GROG' is derived from the British Royal Navy's nickname for Admiral Edward Vernon, who was known as 'Old GROG' due to his habit of wearing a grogram cloak. GROG is typically served warm or at room temperature, and is often garnished with a slice of lemon or lime.