What's the meaning of Orthogonal persistence

I learn the concepts of Dfinity. I’m interesting at Orthogonal persistence, I don’t understand why called it as Orthogonal.

Orthogonality” means

avoid deleterious superfluities;
avoid redundancy

Is that to say Internet Computer will keep the number of same data’s replica within a reasonable range to avoid too many redundancy?

It has nothing to do with redundancy. It just means that you do not need to worry about setting up a database or explicitly save the state. It is done for you automatically.