Origin: Norwegian, Latin, Breton, English
Meaning: not the easiest name to find any information on. The closest I could find was that it is a placee name in Norway though I couldn't find a meaning behind the name.
Maelum could also be a variant spelling of mălum from Latin meaning "evil, wrong" though it's also related to a nearly identical word, mālum meaning "apple".
Maelum could also be an elaborated form of Mael, from Breton Maël meaning "prince" or "chief".
It also comes from an Old English word mǣlum meaning "at a time" from mǣl (time, measure).