“Nickel” is a rascal....
The word "nickel" dates back to the 1750s in Sweden and Germany. One meaning of the German word "nickel" is "rascal," so "kupfernickel" could be translated "false copper." Miners invented this name because nickel ore looks like copper, a more valuable metal. Sometimes the miners thought they had found copper, but they were fooled by that rascally nickel.