A tilted horizon reads as instinctively unsettling — the brain expects level. Roll the camera a few to a few dozen degrees off-axis and what used to be horizontal and vertical lines turn diagonal, carrying that unease straight into the frame.
The name is likely a mangled translation of "Deutsch" (German) — the technique shows up constantly in 1920s German Expressionist film, and the name warped on its way into English usage.
Tilt it too little (under 5 degrees) and it can just read as a mistake; tilt it all the way to 90 and the intent is obvious but heavy-handed. Somewhere around 15 to 30 degrees usually reads as deliberate unease rather than an accident.
When to use
Reach for it at a moment of tension, confusion, or psychological distortion — briefly, not for a whole scene. Use it in every shot and it stops reading as style and starts reading as a mistake.