Everyone seems to agree that CVID is the key acronym to watch for as Donald Trump and Kim Jong-un prepare to meet for landmark nuclear talks, but it’s less clear what it actually means or even what it stands for.

Complete (or sometimes Comprehensive), Verifiable, Irreversible Denuclearization (or maybe Dismantlement) is what the U.S. side is insisting on from the North Koreans at the meeting. “We’re calling it CVID now,” State Department spokesperson Heather Nauert told reporters last month. “Because the State Department, the government, likes acronyms so much, we’ve got a new one: CVID—complete, verifiable, irreversible denuclearization. That is our policy and that is the policy of Secretary Pompeo.”

Pompeo has indeed repeatedly used the phrase, though he also has confused things by referring to “permanent, verifiable, irreversible dismantling.” Both the U.S. and South Korean governments have insisted there’s no difference between CVID and PVID, but what exactly the D stands for is more dicey.

Contrary to what Nauert suggested, the Trump administration didn’t coin CVID. “Complete, verifiable, irreversible dismantlement” was a mantra for the George W. Bush administration in its dealings with North Korea over its nuclear program. The phrase distinguished Bush’s approach from Bill Clinton’s, which he had criticized on the campaign trail. Under the 1994 Agreed Framework, North Korea had agreed to freeze its nuclear program. But for various reasons, including a U.S. failure to follow through on its own commitments, the deal fell apart, and North Korea resumed its program.

Bush, the CVID concept suggested, would settle for nothing short of North Korea dismantling its program entirely so that it could never be reconstituted. “[Bush’s CVID] is not a real policy. This is a partisan posture,” said Jeffrey Lewis, an expert on nuclear nonproliferation at Middlebury college and founder of the Arms Control Wonk blog. North Korea, not surprisingly, never agreed to Bush’s maximalist position—when the Bush administration eventually struck a deal with the North Koreans in 2007, it referred to “disablement” of its nuclear facilities, a step short of dismantlement. Even that deal proved short-lived.

Lewis recalls that in the Bush years, the CVID formulation was a “favorite of John Bolton,” who is now Trump’s national security adviser and played a not particularly productive role in the lead-up to these talks. That incarnation of CVID is similar to the “Libya model” that Bolton has recently and controversially referred to: North Korea gives up its weapons, completely dismantles its nuclear program, and allows foreign inspection, then it gets better relations with the outside world, including an end to sanctions and diplomatic recognition.

Denuclearization, particularly when phrased as “denuclearization of the Korean Peninsula,” is, as I’ve written before, a vaguer and more contested concept. As Victor Cha, a North Korea expert who served in the George W. Bush administration and was briefly considered for appointment as Trump’s ambassador to South Korea, recently told Congress, the North Koreans “use it to mean, sometime in the future, they believe that the Korean Peninsula should be free of weapons—when there is no longer any threat in the world to North Korea.” In the meantime, they’d like to see a removal of U.S. forces from the region and an end to what they see as hostile military actions by the U.S. that require them to have a nuclear deterrent.

North Korea is “bargaining to gain acceptance of its nuclear program,” noted Lewis. That is not necessarily inconsistent with a commitment to eventually, at some undefined date, give up those weapons, just as the U.S. is theoretically committed to move toward complete global disarmament as a signatory to the Non-Proliferation Treaty.

In fairness to Trump and Pompeo, they were not the first to change the D in CVID to denuclearization; the Obama administration sometimes did that too. But in the context of the lead-up to these meetings, it’s significant that Pompeo has more or less combined the concepts into one.

“To turn it into CVI–Denuclearization of the Korean Peninsula is insane,” said Lewis. “It doesn’t mean anything. It’s these two concepts that don’t go together. It’s an oxymoron.”

What it actually may mean is that Trump potentially gets to come out of this meeting with something he can sell on Twitter and at rallies with his supporters as a major North Korean concession, while North Korea doesn’t actually give anything up. The more ideological Bolton won’t like this, but Pompeo seems keen on making it happen.

“Trump wants this summit and he’s going to do whatever it takes to make that happen,” said Lewis. “And if that includes, agreeing to the ‘complete verifiable, irreversible, denuclearization of the Korean Peninsula,’ he’s ready to sign.”