Nickel

Cronstedt studied under Brandt, who isolated cobalt, and isolated another metal from ore that was neither copper nor cobalt. Colloquially known as kupfernickel by miners, he dubbed it nickel for short. Turned out nickel was also magnetic but weaker than iron.
 Axel Fredrick Cronstedt Sweden 1751 Nickel

Cronstedt studied under Brandt, who isolated cobalt, and isolated another metal from ore that was neither copper nor cobalt. Colloquially known as kupfernickel by miners, he dubbed it nickel for short. Turned out nickel was also magnetic but weaker than iron.