Knight of the Wood or Knight of the Mirrors. So called because his coat was overspread with numerous small mirrors. It was Sampson Carasco, a bachelor of letters, who adopted the disguise of a knight under the hope of overthrowing Don Quixote, when he would have imposed upon him the penalty of returning to his home for two years; but it so happéned that Don Quixote was the victor, and Carrasco's scheme was abortive. As Knight of the White Moon Carrasco again challenged the Manchegan lunatic, and overthrew him; whereupon the vanquished knight was obliged to return home, and quit the profession of knight-errantry for twelve months. Before the term expired he died. (Cervantes: Don Quixote, pt. ii. bk. i. 11, etc.; bk. iv. 12.)
Don't cry [or halloo] till you are out of the wood. Do not rejoice for having escaped danger till the danger has passed away.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894