The word Nightcap has a few different meanings.
Originally, it referred to a piece of clothing worn for sleep, presumably to keep one’s head warm.
Over time, it came to be used as a slang expression for an alcoholic beverage drank right before bed, again presumably to keep one’s body warm.
Finally, “Nightcap” can also refer to the final race or contest of a day’s sports. Over the time, this sense had morphed into its current slang meaning, used to refer to hooking up with someone.
No matter the meaning, the word conjures up images of cozy evenings spent winding down for the night.
The origin of “Nightcap” dates back to the Middle Ages in Northern Europe and the British Isles, where it was used to refer to a cap worn in bed at night.
The slang version of the phrase, however, referring to an alcoholic drink usually taken before going to sleep, is attested to originate from 1818.
Its third meaning, used in sports, was first documented in 1924, and has been a popular phrase in baseball.
The phrase “Nightcap” has seen a slow decline in usage over the years. Historically, it was used to refer to either a form of headwear or an alcoholic beverage. Today, neither form of the phrase is widely used.
“Nightcaps” appear in cartoons and fictional media, like movies and books, but they have fallen out of favor in the fashion world long ago. Similarly, “Nightcap” as an alcoholic drink is still considered a witty and funny name for a drink; however, it is also not as prevalent as in earlier centuries.
The only thing keeping “Nightcap” going is the association of getting laid with excercise and sports. Since the turn of the 21st century, “Nightcap” has been a popular slang expression, used synonymously to a booty call.
All in all, “Nightcap” is an archaic expression of a bygone age, which managed to adapt to our modern lives through evolving and forming to our needs and uses.