Nightcap (beverage)
A nightcap is an alcoholic beverage consumed right before going to bed. The alcohol content is higher than a wine or beer drink, usually a liqueur or spirit. Traditional nightcaps are brandy or bourbon or a cream-based liqueur such as Irish cream. However wine or beer can often be considered a beverage of choice before bed as well.
The origin of the word "nightcap" is not fully known but there are two theories. First, the warming and dizzying sense of alcohol before bedtime may help some sleep, thus putting a "cap" on the night. Another theory is related to the actual clothing "nightcap", which was a garment worn to keep the head warm, in times when there may not have been sufficient heating. The same way that the garment kept the wearers head warm, the alcohol "nightcap" had a similar effect.