Rocinante is the name Don Quixote gives to his horse. It is a broken-down nag, a hack, but in his distorted imagination he thinks it is a beautiful, noble animal worthy of a valiant knight like himself. The author, Miguel de Cervantes Saavedra, tells how Don Quixote names the animal in Chapter One.
Four days were spent in thinking what name to give him....he decided upon calling him Rocinante, a name, to his thinking, lofty, sonorous, and significant of his condition as a hack before he became what he now was, the first and foremost of all the hacks in the world.
Like Don Quixote himself, Rocinante is old and feeble. Together they make a ridiculous pair. Yet Don Quixote sees himself as a handsome, strong and fearless knight and Rocinante as a noble-looking horse well suited for such a rider. In illustrations for Cervantes' world-famous book, Rocinante is usually depicted as swaybacked and skeletal.
John Steinbeck named his specially made camper "Rocinante" after Don Quixote's horse at the start of the long journey he made across America with his poodle Charley, which he recorded in his book Travels with Charley: In Search of America (1962). Steinbeck was getting old and had health problems. This made him identify with the still dauntless old Spanish knight.