How did echinoderms get the name meaning spiny skin?

The name "echinoderm" is derived from the Greek words echinos, meaning "spiny" or "hedgehog-like," and derma, meaning "skin".12

This name was coined by the German naturalist Jacob Theodor Klein in 1734 to describe the phylum Echinodermata, specifically referencing the characteristic projections or spikes that extend from the internal skeleton of many of these animals, such as sea urchins. While these spiny projections are a defining feature for many members of the phylum, it is worth noting that the surface texture of other echinoderms, such as sea cucumbers, is often merely warty rather than spiny.12