What is a red eye coffee?
Red eye coffee, also called a 'shot in the dark', is a cup of filter coffee topped with a single shot of espresso. It is commonly attributed to Starbucks, and while it may be true that Starbucks popularized the term, the drink has been around for much longer.
A variation of the drink with two shots of espresso is commonly called a 'black eye'. The three-shot variation is referred to as a 'dead eye', 'green eye', or another name that tactlessly references a tragic moment in US history.
Origins of a red eye coffee
The recipe for a red eye coffee is simple — just brewed coffee with an espresso shot. So it's likely that someone mixed espresso with filter coffee shortly after the invention of the espresso machine in the early 1800s.1
Other names for red eye coffee
Red eye isn't a popular order, and so it is isn't a widely used term. However, for those with knowledge of the drink "red eye" is the most common name for it.
Other names are used throughout the USA, including shot in the dark, oil spill, and sludge cup.
Some brands have their own name for the drink, for instance at Dunkin' Donuts it is called a "Turbo Hot coffee".2
Caribou coffee call it a "depth charge".3 They are very protective of this name and willing to sue you if you use it!4
The origins of the term red eye
We've now done more research on the etymology of red eye coffee than we intended — and have found three possible origins.
The first two are commonly cited origin stories — that the term comes from red eye flights, or that the coffee simply makes your eyes red.
The third origin comes from our own research — it sounds absurd at first, but may well be the true origin of the term — it is a type of gravy made with coffee.
We haven't been able to confirm any of these theories!
Red eye flights
The popular explanation for the origin of 'red eye' in reference to coffee is both simple and plausible. This very strong coffee might be your choice if you're preparing for a red-eye flight — a relatively short flight departing at night and arriving in the morning
It gives you red eyes
The theory that it's named for its effect of causing red eyes is also conceivable. The other two theories seem more compelling.
Red eye gravy (our theory)
While researching for this article, we stumbled upon lots of references to red-eye gravy — a pork gravy made with coffee! Could it really be a coincidence that two separate coffee based liquids have the same name?
Red eye was typically served with a ham with a round bone in the center — which is where it gets the name red eye. Pork with red eye gravy was a well known dish5 served in diners — popular with truck drivers.6
So, how would the name of a gravy come to mean an espresso and filter coffee mix? Truckers, who would have needed a strong coffee for the road, would refer to the thick brown drink as "red eye", as it resembles gravy.
This becomes less far fetched when you consider other diner slang for the same drink — in Alaska it is known as a "sludge cup" and in Ulysses, Kansas it is called an "oil spill". "Mud" and "dirt" are also slang for coffee.
We think could be the etymology of the term — if not, it is a big coincidence — but that is purely speculation on our part. If anyone can debunk or prove this theory we'd love to hear about it!