Describe the Artful Dodger in Oliver Twist. Why was he given his nickname?

In Oliver Twist, Charles Dickens introduces a young pickpocket named Jack Dawkins who most people refer to him as "the Artful Dodger" The nickname describes his skill at his trade: his mind is cunning, his fingers are sly, and he's quick on his feet—making an "art" out of thieving on the crowded London streets.
The Artful Dodger is the young leader in Fagin's gang of street urchins. Although he's only a child, like Oliver, he carries himself as someone much older, as Dickens describes:

He was a snub-nosed, flat-bowed, common-faced boy enough; and as dirty a juvenile as one would wish to see; but he had about him all the airs and manners of a man . . . He wore a man's coat, which reached nearly to his heels. He had turned the cuffs back, half-way up his arm, to get his hands out of the sleeves: apparently with the ultimate view of thrusting them into the pockets of his corduroy trousers; for there he kept them. He was, altogether, as roistering and swaggering a young gentleman as ever stood four feet six, or something less, in the blushers. (chapter 8)

Life on the streets has hardened the Artful Dodger, and he does what he must to survive. He befriends Oliver and attempts to train him as a pickpocket, though Oliver doesn't have the knack or the heart for it.
After betraying Oliver, the Dodger gets caught at last for a simple theft of a snuff-box. His reputation for being particularly adept at pickpocketing is demonstrated as his fellow thieves pay tribute to him; the Artful Dodger is going to be sent away to Australia, as many Victorian criminals were. Charley Bates expresses to Fagin his regret that the boy didn't get caught at a glorious crime more worthy of his name:

"To think of Jack Dawkins—lummy Jack—the Dodger—the Artful Dodger—going abroad for a common twopenny-halfpenny sneeze-box! I never thought he'd a done it under a gold watch, chain, and seals, at the lowest. Oh, why didn't he rob some rich old gentleman of all his walables, and go out as a gentleman, and not like a common prig, without no honour nor glory!"
With this expression of feeling for his unfortunate friend, Master Bates sat himself on the nearest chair with an aspect of chagrin and despondency.
"What do you talk about his having neither honour nor glory for!" exclaimed Fagin, darting an angry look at his pupil. "Wasn't he always the top-sawyer among you all! Is there one of you that could touch him or come near him on any scent! Eh?"
"Not one," replied Master Bates, in a voice rendered husky by regret; "not one." (Chapter 43)

The Artful Dodger earns admiration and respect from his fellow thieves due to his gift for pickpocketing, his swaggering attitude, and his defiance until the end.
At his court hearing, the Artful Dodger is deemed guilty of theft, but—believing England is to blame for his poverty and subsequent life of crime—he protests: "I am an Englishman; where are my privileges?" As he's led off to his fate, Dickens describes the Dodger as "grinning in the officer's face, with great glee and self-approval." Though he may be a thief, the Artful Dodger is proud of his skill and his trade.