Dewclaw

A dewclaw is a digit – vestigial in some animals – on the foot of many mammals, birds, and reptiles. It commonly grows higher on the leg than the rest of the foot, such that in digitigrade or unguligrade species it does not make contact with the ground when the animal is standing. On dogs and cats the dewclaws are on the inside of the front legs, positioned analogously to a human thumb. Although many animals have dewclaws, other similar species do not, such as horses, giraffes and the African wild dog.

The name refers to the dewclaw's alleged tendency to brush dew away from the grass.