It has lost it's original meaning, and is now a colloquial phrase meaning "outside the limits of acceptable behavior or judgment."
The Norman conquest is ancient history now, if someone is offended I suspect they are just too easily offended or simply trolling.
Follow
Shows how much I know about history, it's actually what an article I was reading called the "other norman conquest", in the 14c of ireland, not the actual norman conquest.
Still ancient history, point still stands.
