nickel

English nickel comes from German Nickel, coined by mineralogist Axel F. Cronstedt as shorthand for Kupfernickel, literally "copper goblin" — from Kupfer (copper) and Nickel, a nickname for a mischievous or insignificant person. That nickname was itself a pet form of Nikolaus (Nicholas), which traces back through Latin Nīcolāus to Greek Νῑκόλᾱος, built from νῑ́κη (victory) and λᾱός (people).

The name started as a personal name meaning something like "victory of the people," but by the time it reached German mining slang it had curdled into a term for a trickster or goblin. Miners called the copper-colored ore Kupfernickel because it seemed to promise copper but yielded none — a goblin's trick — and Cronstedt shortened that grumble into the element's name.

It's a linguistic cousin of cobalt, which comes from German Kobold (goblin) for the same reason: both metals were blamed on mischievous spirits when their ores disappointed miners expecting more valuable stuff.