Sour cocktails incorporate liquor + citrus juice + sweetener — and were probably invented by the British Navy. In order to combat scurvy, British sailors would mix lime juice (hence the term “limeys”) with rum, which was readily available in the Caribbean, to make “grog.” But be careful, too many and you’ll be “groggy” in the morning.

The use of egg whites in cocktails dates back to at least 1862 when it was mentioned in the classic “Bartenders Guide” by Jerry Thomas. Much in the same way butter mellows vinegar in hollandaise, egg whites tame the citrus in sours.