Caliban is a character in Shakespeare’s play The Tempest. He lives on the island before Prospero arrives; Prospero then keeps him as a slave. The play paints him as rough and ugly in shape — “only half human” in the old stage picture — because his mother, Sycorax, is a witch and his father is said to be a devil. He is not a real man from history; he belongs to the play. Later writers sometimes say “a Caliban” for someone they want to call brutish or untaught, though that use is literary and a bit unkind. Though actually, in the play he is more than a monster: he knew the island first, and he is angry at being ruled.