The prototypical picaro normally finds himself in a cruelly unyielding world where he must simultaneously serve the needs of several masters. So numerous are these competing demands that, in order to survive, he invariably becomes a master of deception, simulation and multiple disguise.
-- William Makepeace Thackeray, Vanity Fair, 1848
He is rich, this picaro, O'Brien. But there is, also, a proverb — that no riches shall avail in the day of vengeance.
-- Joseph Conrad, Ford Madox Ford, Romance, 1903
Picaro came to English from Spanish in the 1600s, though the etymology of this term is disputed.