1911 Encyclopædia Britannica/Dew-claw

DEW-CLAW, the rudimentary toes, two in number, or the “false hoof” of the deer, sometimes also called the “nails.” In dogs the dew-claw is the rudimentary toe or hallux (corresponding to the big toe in man) hanging loosely attached to the skin, low down on the hinder part of the leg. The origin of the word is unknown, but it has been fancifully suggested that, while the other toes touch the ground in walking, the dew-claw merely brushes the dew from the grass.