Pretty sure they are germanic in origin, but I would have to double check.
Originally, in the middle ages miners experienced toxic gasses and other weird effects while mining iron, such as ore exploding when smelting. They attributed some of the problems to mischievous creatures they would call Kobolds hiding in the mines.
It was eventually discovered that these problems were caused by another whole element creating impurities in the ore, when separated and identified, it came to be known as Cobalt.