"Concatenate" seems redundant to me, as the Latin prefix "con" means "together" and the root "caten" is a chain. So technically it's "chain together", but a chain is already a thing that is linked together.

My Latin is rusty, but IIRC "con" can optionally just be added for emphasis, e.g. "iacere": to throw, but "conicere":to hurl. Maybe that's what was done here.