plural of nickel, a U.S. coin worth five cents, or the metal element nickel.
From Swedish 'kopparnickel' (copper demon), because miners found a deceptive ore that looked like copper but wasn't. German simplified it to 'Nickel,' and when the five-cent coin was introduced in 1866, it was named after its nickel content.
Medieval miners thought nickel ore was cursed—it looked valuable but wouldn't yield copper, so they blamed a demon ('Old Nick') for tricking them. That angry name stuck, and now we carry 'devil coins' in our pockets!
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