Why are the plates called tectonic plates

The plates called Plate tectonics as it is the assumption that Earth's exterior crust is split into many plates. The plates slide over the blanket and the rocky interior layer over the center. It appears like a solid and unbreakable crust in contrast to Earth's mantle. The plates are described after the landforms discovered on them and there are nine significant plates.

Plate tectonics is the theory that the Earth's outer shell is divided into many plates the glide over mantle. The plates act like a hard and rigid shell in contrast to the Earth's mantle.