The name originally comes from cigars known as blunts. The most famous brand was Phillies blunts, which were popularized with both west and east coast rap in the early nineties. See the chronic and dr. dre for more info. In 2000 most blunt smokers have found themselves switching to Dutch masters aka dutchies which have real tobacco leaf casing. Although not officially blunts, the idea is the same.
L and blizzie are also occasional slang terms for blunt.
The rolling of a blunt requires what is often called cracking the blunt. With a traditional Phillie pros will crack using their thumbnails, but the amateur will often use a knife or a razor blade. After the blunt has been cracked, the tobacco can be removed, and then the marijuana added. The separate papers must be licked sufficiently and then rolled one first, and then the next over top. Variations such as the honey blunt will have to be dealt with later. Dutchies can be unwrapped as well as cracked.