On Sept. 10, 2001, the edgy comedian George Carlin did a bit in whch he said: “Would you like me to tell you about something I really like? Fatal disasters. Fatal disasters with a lotta dead people.” (Wyatt Counts/Associated Press)

On Sept. 10, 2001, on a stage in Vegas, a city he loathed, George Carlin performed the red-hot closing bit he planned to use for his latest HBO special. “Would you like me to tell you about something I really like?” he teased the crowd at the MGM Grand. “Fatal disasters. Fatal disasters with a lotta dead people.”

He called the 10-minute closer “Uncle Dave” and it came after Carlin had done an Osama bin Laden, airplane explosion joke earlier in the set. Ah, the difference a day makes. He named the bit not for a real uncle, but for a cosmic, doomsday scenario in which Earth collapses and disgruntled Uncle Daves everywhere are redeemed. Carlin loved the closer enough to make its key line — “I Kinda Like It When a Lotta People Die” — the title of his special. The poster had even been designed. And then the attacks.

Carlin reworked the material in his set, added other bits, and, that November, HBO aired a different live special called “Complaints and Grievances.” He put “Uncle Dave” on ice or, more specifically, in a box with dozens of other live cassettes he collected until his death in 2008.

Now, 15 years after 9/11, his daughter, Kelly, longtime manager Jerry Hamza and archivist Logan Heftel are putting out “Uncle Dave” as well as other portions of Carlin’s sets from Sept. 9 and 10 on “I Kinda Like It When a Lotta People Die.” The set is now playing on Sirius XM and arrives on CD and vinyl on Sept. 16.

“I’m pretty positive that this is the only time he ever went, ‘Yeah, probably not appropriate for the culture right now,’ ” says Kelly Carlin.

George Carlin, recipient of the Lifetime Achievement Award, arrives at the 15th American Comedy Awards at Universal City in Los Angeles on April 22, 2001. (Kevin Winter/Getty Images)

That a comedian shelved such unforgiving material after 9/11 may not seem surprising, unless you consider the source. Carlin was not one to back down when it came to his work. He did school shooting jokes after Littleton, mocked his Vegas crowds to the point that audience members would stream out, and he had never before let a piece go because he feared it might offend someone.

Remember, this is a man who made great sacrifices for his art. In the 1960s, Carlin was a clean-shaven comic in a neat suit making gobs of money with bits like the “Hippie-Dippie Weatherman.” But he felt trapped, disgusted by the government and inspired by the protest movement. He grew his hair, smoked dope and developed searing material meant to question virtually every aspect of society. He famously created “Seven Words You Can Never Say on Television” and, after a concert in Milwaukee in 1972, was arrested for obscenity.

But by then, he was a star and counterculture hero. Carlin hosted the first episode of “Saturday Night Live” in 1975, taped the first of 14 HBO specials in 1977 and eventually wrote a series of best-selling books. He also didn’t soften. In fact, he got tougher and less forgiving as he got older. He attacked consumerist culture so passionately he left his audience bruised or disgusted. What kept him on top is that he always managed to be funny.

I spoke to Carlin only once, in 1999, and pressed him on a school shooting bit, which he did the night of the Columbine High School massacre in Littleton, Colo.

“How can you still do that joke?” I asked.

“Boy, you need that joke more than ever now,” he said. “The artificial weeping in this country, this nationwide mourning for dead people is just embarrassing, and these ribbons and these teddy bears and these little places where they put notes to dead people and all this s---. This is embarrassing and unnecessary, and it just shows how immature, how emotionally immature the American people as a class are.”

Carlin was in Las Vegas on the morning of the World Trade Center attack.

“George hated doing Vegas,” says Hamza, who managed Carlin for more than 30 years. “He did it for the money, but he hated the audiences. He thought they were stiffs mostly. It was a lonely deal for him. He had a condo, but he didn’t like being there.”

“Every show in Vegas, at some point, maybe a quarter, maybe a third of the audience would start to trickle out,” says Kelly Carlin, who attended one of the shows that September. “Sometimes it would be the first time he said, ‘c---.’ Or people would say, ‘wasn’t he the Hippie Dippie Weatherman?’ And then he’d start in with an abortion joke. These people were unprepared, and it was always heartbreaking for me. And I could see my Dad onstage. I don’t think other people could see but being a daughter and knowing every little micro-expression on my Dad’s face, you could see this hardening in his body and the anger would come up. He had a great disdain for people who couldn’t handle his darker material.”

“Uncle Dave,” the closer, was as dark as it gets.

In “rooting for a high death toll,” Carlin ticks off the pros and cons of a variety of natural disasters, everything from tornado and a famine to an asteroid, with the precision, energy and slow build of a master conductor leading an orchestral performance of “Bolero.” In his scenario, a massive fireball consumes all, including soccer moms and guys named Todd.

“I don’t care who gets killed,” Carlin declares at one point. “As long as it’s not me or someone close to me. Although to tell you the truth, if it’s a nice, big disaster, something good, the people close to me are on their own . . . . It’s not my responsibility.”

There are reams of tapes in Carlin’s boxes, with handwritten notes detailing where material shifted and which recordings were most important. Along with the Vegas material, archivist Heftel, who is 30 and never met Carlin, added a clip converted from a reel-to-reel tape the comedian made at home in 1957, when he was just 19. Putting out the Vegas material offered some technical challenges, Heftel says, mainly removing hiss without deadening dynamics.

Hamza said he wasn’t surprised Carlin put aside “Uncle Dave” and reworked his material for the special after 9/11.

“George was from New York,” he says. “He grew up on West 121st Street. He loved New York City. Anytime we got within a 100 miles of New York, we would work out of New York. All he wanted to do was walk around New York all day. He just loved that. When 9/11 happened, that really went right in the league with the Dodgers leaving. It was heartbreaking for him. He got angry. He was angry, but then I think he was just sad that it could happen in New York.”

That said, Carlin told him he expected “Uncle Dave” would one day be back.

“George always felt that nothing would go to waste,” says Hamza. “Sometimes we would put the show together and we wouldn’t have room for this two- or three-minute piece, and he’d say, ‘don’t worry about it, we’ll get to use it.’ ”

And he did — sort of. Carlinophiles will recognize parts of the original closer harvested for “Coast-to-Coast Emergency,” the final bit on the 2005 HBO special, “Life Is Worth Losing.” But hearing “Uncle Dave” in its intended form is eye-opening. Next to it, “Coast-to-Coast” feels flatter, muted, less committed as he focuses on weather disasters. “Uncle Dave” is fast, harsh and far, far darker. (“I Kinda Like It When a Lotta People Die” features material never heard, though close listeners will again hear that Carlin reworked some of the elements for future releases.)

“I Kinda Like It” is also not likely to mark a flooding of the archival release market. There simply isn’t much in Carlin’s tape boxes that he didn’t use. Kelly Carlin imagines there could be future releases with historic significance, say the ’72 Milwaukee show. There are also plans to finally release one of Carlin’s own pet projects, an album he liked to refer to as “Carlin Comes Clean.” It would be just that: Clean.

Kelly Carlin is asked what she thinks her father would think of “Uncle Dave” finally coming out.

“You have to look into your own heart,” she says. “It is eight years later. We’ve taken our time with it. And been thoughtful about it. And I can also hear my dad’s voice, in my head, saying something like, ‘I’m dead. I don’t get to be part of the conversation.’ ”

An earlier version of this story misstated the name of George Carlin’s 2005 HBO special, “Life Is Worth Losing.”