My source SAOB also says Dutch maalstroom is the origin. See the new Swedish entry malström.
Maalstroom is the modern Dutch spelling. aa often used to be spelled ae a few hundred years ago, but that's not done anymore except in some old names. The word maalstroom itself probably comes from malen (to grind) + stroom (stream).
Dutch Wikipedia has an article named w:nl:maalstroom, but none named maelstroom.
Seems like w:nl:Moskstraumen has the complete story: Maalstroom is/was the Dutch name of the Moskstraumen, a tidal stream in the Norwegian sea. It used to mean whirlpool, but the modern word for that is draaikolk.
See also w:Talk:Maelstrom#Etymology, w:Talk:Maelstrom#Etymology, again. I am not terribly convinced that Dutch cartographers gave it its name (Atlas Cosmographicae (Mercator) gives Maelſtrom), see e.g. w:Grottasöngr#Prose Edda, a name is often (much) older than the legend trying to explain it.