Why is the question mark crooked?

Dictionary of German colloquial language
Question mark
Question mark n \
1. Hunched posture. It mimics the shape of a question mark. 1910 ff.
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2. shitty (shitty, crooked shit) Question mark = People with very bad posture. Sounds like the barracks yard jargon of the trainers. ⇨ Question marks 7 and 8. 1910 ff.
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3. bent Question mark = Person in very bad posture. 1935 ff.
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4. walking Question mark = ugly (incompetent) person who does not fit into their environment or who cannot be categorized. One wonders what she wants in the relevant place or in these social circles. 1935 ff.
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5. skewed Question mark = curved standing person; Soldier in non-military posture. Ziv and sold 1910 ff.
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6. as a Question mark standing there (walking or similar) = standing in bad posture (walking or similar). 1910 ff.
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7. like a shit Question mark stand there = stand in a bad military posture. Pay 1910 ff.
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8. like a shit in the air Question mark stand there = stand crooked. Pay 1910 until today.
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9. a Question mark have in the voice = speak questioningly. 1960 ff.
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10. like a living one Question mark lying = lying curled up in bed. 1910 ff.