The term 'ankle horse' is a combination of three words: HOCK (4 letters), TARSI (5 letters), and tarsal (6 letters). HOCK refers to the joint between the hind leg and the foot of a horse, which is analogous to the ankle in humans. TARSI is the plural form of the word tarsus, which is the group of seven bones in the human foot that make up the ankle. Finally, tarsal is the adjective form of tarsus, meaning pertaining to the tarsus. Together, these three words describe the anatomy of the ankle in both horses and humans.