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And as an auxiliary with bare infinitive: don't; (you) mustn't. Frequently used humorously in phrase "moenie panic (also worry) (nie)": don't panic, don't worry.
Early 20th century; earliest use found in Charles Pettman (b. 1851). From Afrikaans moenie —— (nie) must not, do not ——, shortened from Dutch moet niet from moet + niet.