For me the connection between categorical limits and calculus appears when you can define an iterative process, expecially if a category is a poset or is filtered.
For instance, you get a fixed point of an algebra by iterating the powers of a functor. Or you are defining smaller and smaller neighborhoods using sieves or sigma-algebras (hence integrals).
I realize this is handwaving, but categorical nomenclature evolved by generalizing concrete concepts from other areas of math.