Possibly a calque from Taiwanese 菜鸟, which parallels the Minnan word for new military recruits. Note: 菜鸟 is also the brand name of Alibaba's logistics company (Cainiao Network).
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Mild, usually self-deprecating or gently teasing. Harsher equivalents: 弱鸡 (weak chicken), 手残 (cripple-handed). Contrast with 大佬 (veteran / pro).
