nachtentach
When you see a German who works like a maniac at night and snoozes like a baby all day. You have to greet them with this word or they'll give you the evil eye.
Hey bro, you're gonna have to say 'nachtentach' or I'm gonna curse your Wi-Fi.
I met this German at the bar and forgot to say 'nachtentach', now I have a hangover and a bad luck charm.
My cousin's German friend yelled at him for not saying 'nachtentach', now he's sleeping in the garage.