Why are Isopods called pill bugs?

Isopods are commonly referred to as pill bugs due to their ability to roll into a ball when threatened, a behavior that resembles the shape of a pill. This defensive mechanism helps protect them from predators. The name "pill bug" specifically refers to the terrestrial isopod species Armadillidiidae, which has a rounded, segmented body that facilitates this rolling action. Their ability to curl up is a distinctive characteristic that sets them apart from other isopods.