What does 'rock of ages' mean?

Question

I don't mean the Def Leppard song or the cliff in Burrington Combe, England, but 'rock of ages' as an expression. I read it on a novel but I can't find it in any dictionary (I'm portuguese). It seems to me it could be some special rock formation where geological layers are very visible, but I'm not sure. Does anyone have an idea? Thank you!

Answer 1

Its religious.