It’s ironic that Carly Simon’s biggest hit “You’re So Vain” was on an album titled No Secrets. After all, the inspiration for the song has been one of the biggest secrets in popular music history — and even today, the mystery has only been partially revealed.

The staggering success of the song has deepened the guessing game. After receiving the Best New Artist of the Year Grammy in 1971, Simon released “You’re So Vain” in November 1972 — the track quickly skyrocketed up the Billboard chart, where it stayed for 17 weeks, peaking at No. 1 on January 6, 1973.

The lyrics of the meta song pointedly accused someone — likely a lover — of being way too into himself. And with Simon’s famous lineup of romantic partners, the cocky individual could have pointed to Warren Beatty, Michael Crichton, David Geffen, Kris Kristofferson, Terrence Malick, Jack Nicholson, Cat Stevens, James Taylor or John Travolta — or even rumored flings with Sean Connery (she later denied any romantic interactions), Marvin Gaye and Jeremy Irons. And of course, there was the possibility of Mick Jagger, with whom she shared “raw electricity” while singing together.

Beatty rose to the top of the list after a 1983 interview with the Washington Post when Simon said, “It certainly sounds like it was about Warren Beatty. He certainly thought it was about him — he called me and said thanks for the song.”

But the sneaky singer didn’t confirm at the time if his appreciation was warranted.

Carly Simon

Carly Simon, 1971

Over the years, Simon's revealed a few of the letters in the subject's name

For decades, Simon remained mum on the subject. But 31 years after the song came out, she finally gave up her secret in 2003 — but only to one person, then-NBC Sports Chairman Dick Ebersol.

An odd recipient of such coveted information, the television executive had good reason to be the co-secret keeper. He donated $50,000 in an auction for Martha’s Vineyard Community Services to earn the rights to the name (which he couldn’t reveal) as well as a private performance over a lunch of peanut-butter-and-jelly-sandwiches and vodka on the rocks, according to the Los Angeles Times.

Ebersol was given one clue in advance: The letter "E" was in the person’s name.

The following year, Simon gave up a few more letters, telling Regis Philbin in 2004 that the letters “A” and “R” were also in the name.

In 2010, she got more detailed in an interview with British music magazine Uncut: “I'm just going to tell you this — the answer is on the new version of ‘You're So Vain. ’There's a little whisper — and it's the answer to the puzzle.”

That whisper, about 150 seconds into the 2009 version of the song sounds a bit like, “David,” with the “a” dragged out, according to the Washington Post. By that time, she had already eliminated famous Davids like David Bowie and David Cassidy.

The second verse is about Beatty

Simon proceeded through life, teasing and dropping hints, but keeping the identity of the arrogant subject to herself. But in 2015, when she was promoting her memoir, Boys in the Trees, she used her secret as ammunition for publicity.

“It was my [book] publisher who called up and said, ‘People Magazine will put you on the cover if you tell who ‘You're So Vain’ is about, or just give one verse up.’” she told the BBC.

So she did: “I have confirmed that the second verse is Warren.”

In a moment when the world should have rejoiced for finally getting the answer, Simon cleverly tucked in there that perhaps it was actually the plural form of “you” and that the first and third verses were about other people.

When asked if Beatty knew it was about him, she added, “Warren thinks the whole thing is about him!”

And she added more mystery to her loophole. “Now, that doesn't mean that the other two verses aren't also about Warren,” she told the BBC. “It just means that the second one is.”

Warren Beatty

Warren Beatty, late 1960s or early 1970s

Simon confirms the song is not about Taylor or Jagger

As much as Simon has dropped hints, she’s also eliminated some people, sparing them of the reputation of potentially being vain.

A popular target was Taylor, who she was married to from 1972 to 1983 — including during the release and popularity of the song. But Simon quickly denied it was about him during an interview the couple did together for Rolling Stone in 1973.

It’s definitely not about James although James suspected that it might be about him because he’s very vain,” Simon told the music magazine.

After all, there was a very direct clue in the line, “Then you flew your Learjet up to Nova Scotia.”

Simon explained, “He had the unfortunate experience of taking a jet up to Nova Scotia, after I’d written the song. He was saved by the fact that it wasn’t a Lear.”

Taylor jumped in clarifying, “A small twin-prop.” As for his opinion on the song? “Well, I thought it was a nice song. I heard it played on the piano and sung. I didn’t hear the production of it that’s out now. I like the tune. It has an interesting turn.”

Another musician who was spared scrutiny in the early years was Jagger. In a 1983 Washington Post story, Simon simply said, “No.” And she reconfirmed that it wasn’t the “(I Can't Get No) Satisfaction” singer in her book as well.

READ MORE: Carly Simon Was by Jackie Kennedy's Side When She Died. Inside Their Surprising Friendship

A secret fourth verse was revealed in 2015

While she didn’t disclose the whole story in her 2015 memoir, she did unveil a secret fourth verse.

The new lyrics were: “A friend of yours revealed to me / That you'd loved me all the time, [You] kept it secret from your wives / You believed it was no crime.”

In 2017, she performed the new verse from home while playing the piano for the BBC Four’s Classic Albums.

“This is a verse that I haven't ever sung,” she said. “I wrote it a while ago on a pad, but it never made it into the song.”

Simon doesn't plan on revealing the truth

So is the song all about Beatty? Or are there three more famous names out there for each of the other verses? Only Simon knows the truth. And revealing the truth isn’t exactly on her to-do list.

"I would have to want to,” she told ABC News. “I would just have to say, ‘Okay, I’m gonna have to dunk you both into this fever that is people still wanting to know.’ I still can’t understand that!"

While that sure does seem like there are at least two other vain stars, even those in her closest circle don’t know the answer. “We never talked about it,” her manager during the 70s, Arlyne Rothberg told the BBC. “The answer wasn't as important as the game.”