I've always thought of it quite literally.
*Christ died on a Hill (Calvary)(.
So, it is something you feel strongly enough about that you would 'die' rather than change your stance upon it (like Christ was given the chance but chose to die for our sins).
But maybe I am quite wrong and it has nothing to do with that?
No , that's how I would interpret it - something you feel so strongly about that you won't compromise your beliefs .
Be it your DC wearing their seatbelts , never eating meat or any other personal view .
My hated phrases (only ever seen on MN)
"I cannot get worked up about this/simply hven'y got the energy to get worked up about this"
Now I know it means I'm a lazy sod and I just CBA expending any effort
But in my mind its I am so much more chilled and laid back that you , it wouldn't figure on my radar . Take a chillpill