Yin

google

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from Chinese yīn ‘feminine’, ‘moon’, ‘shade’.

wiktionary

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From early romanizations of Chinese 陰／ 阴 (yīn), originally used in reference to shaded areas, as of a mountain or home.

From ān. Cognate with yan, yen, ane and one.

etymonline

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yin (n.)

feminine or negative principle in Chinese philosophy, 1670s, from Chinese (Mandarin) yin, said to mean "female, night, lunar," or "shade, feminine, the moon." Compare yang. Yin-yang is from 1850.