Why does don quixote name his horse rocinante?

"He next proceeded to inspect his hack, which, with more quartos than a real

and more blemishes than the steed of Gonela, that "tantum pellis et ossa fuit,"

surpassed in his eyes the Bucephalus of Alexander or the Babieca of the Cid. Four

days were spent in thinking what name to give him, because (as he said to

himself) it was not right that a horse belonging to a knight so famous, and one

with such merits of his own, should be without some distinctive name, and he

strove to adapt it so as to indicate what he had been before belonging to a knighterrant,

and what he then was; for it was only reasonable that, his master taking a

new character, he should take a new name, and that it should be a distinguished

and full-sounding one, befitting the new order and calling he was about to follow.

And so, after having composed, struck out, rejected, added to, unmade, and

remade a multitude of names out of his memory and fancy, 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"