Jackanapes. Properly “Jack-of-apes,” an impudent fellow who apes the manners of his social superiors. Jackass. The male ass. Jack-boots. When first worn by cavalry these high leather boots were covered with metal plates as a protection for the leg. The term Jack is derived from the Norman-French jacque, a leathern jerkin worn over a coat of mail. At a later period the jacque itself was made swor..