I have googled it and find that it was named by Sir Humphry Davy (who who, you may recall, “abominated gravy, and lived in the odium of having discovered sodium”), and read that :
"Sir Humphry made a bit of a mess of naming this new element, at first spelling it alumium (this was in 1807) then changing it to aluminum, and finally settling on aluminium in 1812. His classically educated scientific colleagues preferred aluminium right from the start, because it had more of a classical ring, and chimed harmoniously with many other elements whose names ended in –ium, like potassium, sodium, and magnesium, all of which had been named by Davy."
So it appears that aluminium is *right.