Why is an arthropod called jointed foot?

Answer 1

The term 'arthropod' comes from the Greek arthro [arthron] (joint) and pod [pous, podos] (meaning foot or leg) hence, the jointed appendages characterization of the phylum. The reason for the name is because of observations about members of the phylum; since they have a hard exoskeleton, the joints about which the hard sections would have to rotate would be on the outside and thus a more obviously apparent characteristic. Contrast with vertebrates with joints on the inside where the bones are located and generally not on the surface, or molluscs, cephalopods, round worms and others without apparent joints owing to their general lack of need for significant rigidity.