What Celebrimbor actually says is Earendil told him his future would be in his son's (Elrond's) hands. It seems a natural place to remember that conversation as Elrond had just secured Celebrimbor's future.
- - - Updated - - -
I'm not 100% sure but weren't the Southlanders moved there after the War of Wrath? I did think it was their ancestral home.
It's also irrelevant, the Witch King wasn't from Angmar, he established Angmar in the Third Age to rival the Numenorean kingdoms.