Kobold comes from the word 'cobalt', which, as I understand it, is German for copper. I'm not sure how English speakers came to use it as the name for another element, or what Germans call that element. Anyway, German miners would dig up what they thought was copper ore, but when it was smelted, what they got was something else which they called 'Devil's copper', or 'Nickel cobalt' in German (as in Old Nick), and English speakers call just 'nickel'. This bait-and-switch was blamed on mischevious cave spirits, which came to known in English as Kobolds. So, long story short ("Too late!"), it's pronounced kO-bald, like cobalt, but with a 'd' instead of a 't'.