In 2010, a woman in Sakura, Japan, posted photos of her well-manicured Shiba Inu to her digital journal. The dog, Kabosu, shot her owner a wide-eyed glance, a comic image that quickly jumped from Tumblr to Twitter to Facebook and to the rest of the internet.

A meme legend was born. Someone on Reddit called the dog “DOGE,” a nonsensical nickname that stuck. Another minted a cryptocurrency in DOGE’s name.

Now, 15 years later, in the fast churn of internet culture, DOGE is considered very old. But try telling that to Elon Musk, who has co-opted “DOGE” for the name of his effort to gut the machinery of the federal government — more formally, the Department of Government Efficiency.

It is one of dozens of old-internet ephemera that are baked into his everyday vocabulary. A brief scroll through Mr. Musk’s X feed reveals a menagerie of aging memes and lingo — dad jokes for the very online. They include:

• Frequent references to “420,” a half-century-old slang term for smoking marijuana said to have started in a high school in Northern California. (After smoking what looked like a blunt live on the Joe Rogan podcast, Mr. Musk briefly changed his Twitter bio to “420.”)

• Regularly including the number “69,” a slang term for a sex act that has been around since at least the Kama Sutra. (Mr. Musk, who is 53 years old, is quick to point out that his birthday falls 69 days after 4/20.)

• Calling things that he supports “epic” or “based.” These are adjectives favored by frequent users of Reddit and popularized by fans of Joss Whedon, a director who created the “Buffy the Vampire Slayer” television series in the late 1990s and went on to direct two of the Avengers movies. (Mr. Musk has said he wants to create “based” artificial intelligence with his chatbot, Grok, and recently told Tesla investors he expected an “epic” 2026 ahead for the company.)

Mr. Musk’s slang may seem inscrutable to people who aren’t steeped in online culture. But to his fans, Mr. Musk’s dated sensibilities are a kind of internet comfort food — and a nod to a shared, aggrieved worldview.

Mr. Musk’s posts are full of the language of warfare and conquest portrayed in video games. That loaded language is a rallying cry for gamers and others from Mr. Musk’s very online world who — if they have a common political ideology — see in him someone who shares their skepticism of authority and their belief that America has gone too “woke.” To them, Mr. Musk’s online updates about what DOGE is up to come across as far more honest than a press release or news conference or — worst of all — something they read in the mainstream media. (It’s a strategy that recalls Donald Trump’s use of Twitter to signal authenticity during his first administration.)

“We’re living in the revenge of the nerds era,” Hasan Piker, a popular, politically progressive online personality who is not a fan of Mr. Musk, said in an interview. “This is the real, actual revenge of the nerds.”

Mr. Musk did not respond to a request for comment.

Every photo of Mr. Musk wielding a chain saw while wearing “deal with it” sunglasses indoors (another meme) represents a triumph of the nerd culture he has long identified with. On Wednesday, he attended the first meeting of President Trump’s new cabinet wearing a T-shirt that said “Tech Support.”

His fans speak back to him in his language. They send suggestions on how DOGE can fix the government by dismantling entire sections of it, often coded in the language of images typically found on Reddit. (Wojak, a crudely drawn character popularized on the message board 4chan, is a perennial favorite.)

Mr. Musk prods his more than 200 million X followers for help with decisions in online polls. And he listens. The conversation becomes a feedback loop of insider jokes for the billionaire, who once hosted “Saturday Night Live” and prides himself on his sense of humor. (Mr. Musk sometimes overestimates his popularity in the comedy world. Once he joined the comedian Dave Chappelle on a stage in San Francisco. He was booed.)

“Anyone can find their own community, even if it’s a community frozen in 2010,” Brian Feldman, an internet culture writer who has long followed Mr. Musk’s exploits, said in an interview.

But to those steeped in modern internet culture, Mr. Musk’s communication style is far from on trend. That is especially so when even current terms like “no cap” (translation: no lie) or “lowkey fell off” (waned in popularity or relevance) are already showing their age. As with recent questions about Mr. Musk’s claims of superior video game skills, they see cracks in his supernerd facade.

“More than people would like to admit, they often become trapped in the internet they first encounter,” Mr. Feldman said.

Last week, Mr. Musk appeared at a conservative political conference wearing dark sunglasses, a big gold chain and a T-shirt that said he was “not procrastinating” but instead working on “side quests” (a common practice in sprawling role-playing games). He played off the quote from the Hindu scripture Bhagavad Gita that Robert Oppenheimer said was going through his mind as he tested the first atomic bomb: Now, I am become Death. The destroyer of worlds.

“I am become meme,” Mr. Musk said to a mostly mute crowd. “There’s living the dream and there’s living the meme, and that’s pretty much what’s happening.”

Even some of his most fervent followers on X recoiled. “Elon Musk fell off lowkey,” one user wrote.

Mr. Musk’s online vocabulary is a reminder of 2010, when nerd culture was ascendant. Reddit was a meme factory for favorites like Lolcats and icanhazcheeseburger. Gamers gathered in web forums or on online role playing games to hang out and fight through digital dungeons.

This was also the beginning of Mr. Musk’s metamorphosis from mere billionaire to internet celebrity. That year, he appeared as himself in the second “Iron Man” film. His online fans ate it up.

All of this also coincided with the rise of Web 2.0, a more social version of the internet. Twitter — long before Mr. Musk bought it and renamed it — was a town square. Facebook moved beyond likes and status updates with “Groups,” a feature that allowed people to form their own smaller communities. The chat forum 4chan was full of anonymous, often angry online trolls who bonded over vulgar behavior.

While online groups had existed for years, the newer social networks were more tightly knit and rewarded the behavior that Mr. Musk often displays today. The right kind of posts could pick up steam and shoot across the internet.

Provocateurs moved beyond small-scale trolling to aggressive mass movements, such as Gamergate, a targeted harassment campaign against a female game designer by video game players who claimed she represented a lack of ethics in games journalism. It morphed into a social movement that fought diversity, feminism and what gamers saw as overly progressive values in film, television, literature and the video game industry — a viewpoint that Mr. Musk shares.

Gamergate also signaled that digital demonstrations could, for better or worse, lead to real-world change.

Mr. Musk’s tweeting style changed from anodyne company updates to more overt trolling. In 2018, he tweeted that he had secured a buyout offer for Tesla for a stock price of $420. Once, when a competing car company tried undercutting him on price, Mr. Musk said that he would drop the cost of his Tesla Model X to $69,420.

“The gauntlet has been thrown down!” he proclaimed on Twitter. “The prophecy has been fulfilled.”

Unlike other tech billionaires, who seemed to live lives far removed from regular internet folk and became less online the richer they got, Mr. Musk was making himself relatable with memes, absurdity and relentless posting. And parts of the online world embraced him.

“Many people find him off-putting, I think,” said coldhealing, a pseudonymous cultural commentator who regularly follows Mr. Musk and other social movements online, in an interview. “But there are many people who he resonates with, and even though I think it’s 10 percent of the population max, it’s an influential 10 percent.”

Mr. Musk’s online life became even more bombastic after the Covid pandemic began in 2020. He attacked Tesla short-sellers and California state officials who wouldn’t let him reopen a Tesla factory. In 2023, he even live-tweeted photos of himself driving to Mark Zuckerberg’s house, threatening to wrestle the chief executive of Facebook. (They were, at the time, in the throes of organizing a real fighting match between them. It never happened.)

He posted himself playing Elden Ring, Path of Exile and other video games like Diablo IV. One of the world’s wealthiest men was telling gamers that he was one of them.

Mark Kern, a former video game executive at Blizzard, wrote in a post to X last week that people should not mess with gamers. “We’re forged by endless boss battles against impossible odds. We do not give up. We do not stop. We are the terminators of the culture war.”

“Yes,” Mr. Musk wrote, quoting the post.

Conservatives who don’t spend a lot of time online have also embraced the image of Mr. Musk taking a chain saw to what they see as a bloated federal government, even if many of them aren’t exactly sure what he’s trying to say or when they’re supposed to laugh.

“It’s validation from people who have no idea what he’s saying, but still think he’s speaking this expert language,” said Mr. Feldman, the internet culture writer.

But Mr. Musk may be finding his online limits. It was difficult for some of his followers to shake off last week’s stage appearance at the Conservative Political Action Conference, which reminded them that it is hard to stay cool when you are, in fact, not very young. (Kabosu did not live to see the meme she inspired enter American political life. The 18-year-old Shiba Inu died last year.)

“Anyone else feel the vibe-shift in tpot/tech?” one X user wrote, referring to an online community called “This Part of Twitter,” which is largely composed of tech workers who have historically warmed to Mr. Musk. In other words, Mr. Musk was starting to look a little out of touch and increasingly unpopular.

Nonetheless, Mr. Musk seems to be doubling down. His posting to X has increased in recent weeks, some days numbering in the hundreds. And he is still being validated by his fans.

On Thursday, Mr. Musk posted another meme to his X account — one of dozens of posts he had made that morning. In it was a photo of Mel Gibson as Mad Max in “The Road Warrior,” the early-1980s action thriller about a shotgun-toting nomad navigating a postapocalyptic world. In bold lettering, the meme said: “Ladies, it’s time to start thinking whether the guy you’re dating has postapocalyptic warlord potential.” (Film buffs may note that Max’s wife and son were killed by a biker gang in the first “Mad Max” film.)

One follower replied with a photo of a man wearing a Trojan helmet and body armor with an assault rifle in one hand and a spear in the other. It was one of more than 7,000 replies.

“Yup,” the follower said, adding a fire emoji.