I was struck recently by the -dom suffix in freedom and kingdom. Not having etymology references at hand, our lunchtime group settled on the theory that -dom in both these words was from "dominion." Dominion is ultimately derived from Latin dominus (lord of the house), if I understand my etymology correctly. It seems to make sense; free from domination is freedom, domination by a king is kingdom.
But it seems that this is not the case. According to Etymology Online, this -dom is derived from Old English dom (judgement, law, statute) and is etymologically close to doom.
I'm really confused by this origin. It seems like the dom- prefix and the -dom suffix should be related. Are they really not, or is it only that my references don't go back far enough or that my etymological understanding is superficial at best? Can someone please clarify the etymology of kingdom, dominion, and doom for me?