What is the root word in cuneiform?

The word "cuneiform" itself is the root word. It comes from the Latin words "cuneus" meaning "wedge" and "forma" meaning "shape."

Cuneiform writing is named for the wedge-shaped marks that were made on clay tablets with a reed stylus.

So, while there isn't a specific root word *within* cuneiform, "cuneiform" itself is the root word for this ancient writing system.