When they were fourteen years old, Dick and Doc were attending an excellent English school where there were a great many future dukes and earls and arch-bishops and lord mayors, who, when they saw how much Dick and Doc resembled one another, called them "The Twins." Later, when they learned that Dick's father was distantly related to Lord Greystoke, who is famous all over the world as Tarzan of the Apes, the boys commenced to call Dick and Doc "The Tarzan Twins" - so that is how the nickname grew and became attached to them.
As everyone knows tar means white in the language of the great apes, and go means black, so Doc, with his light hair, was known as Tarzan-tar and Dick, whose hair was black, was called Tarzan-go. It was all right to be called Tarzan-tar and Tarzan-go, until the other boys began to make fun of them because they could climb trees no better than many another boy and, while they were fair in athletic sports, they did not excel. It was right there and then that Dick and Doc decided that they would live up to their new names, for they did not enjoy being laughed at and made fun of, any more than any other normal, red-blooded boy does.