The original discoverer of the element spelled it "aluminum". The British publisher that published his work changed the spelling. The rest of the world got the right version of the man's work. The Brits are wrong.
It's only the US and Canada that use "aluminum" though isn't it? The rest of the world and most languages have it as "-ium".
Humphrey Davey actually changed his mind and changed it to "-ium" shortly after discovering it.
Also, IUPAC has "Aluminium" as the primary spelling, though both are acceptable.