Knurd

In Terry Pratchett's fictional universe of Discworld, knurd is the opposite of drunk.

Knurd is a state achieved through a special type of coffee. You see life as it really is, for the first time in your life. Few live through the experience without going insane.

Knurdness is the opposite of being drunk, it's as sober as you can ever be. It strips away all the illusion, all the comforting pink fog in which people normally spend their lives, and lets them see and think clearly for the first time ever. Then, after they've screamed a bit, they make sure they never get knurd again.

One type of coffee known in the Discworld multiverse to make you knurd is Klatchian coffee.

"There the men in taverns drink coffee laced with desert orakh. This drink (made from cacti sap and scorpion venom) is one of the most virulent alcoholic beverages in the universe. But the nomads do not drink it for its intoxicating powers, but to mitigate the effect of Klatchian coffee. It made you knurd."

Also, Samuel Vimes, one of the Disc's most notable characters, is sometimes referred to as being constantly knurd, which at least partially accounts for his depressive nature and tendency towards alcoholism - he started out looking for a cure to knurdness.

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Knurd is also said to be one of the origins of the word Nerd.