A national security adviser should probably know what to call the most notorious dictator in the world.

But President Trump's national security adviser Robert O'Brien seemed unsure of North Korean leader Kim Jong Un's name in a Sunday interview with ABC News' Jon Karl. When asked about North Korea's threatened "Christmas gift" that failed to materialize, O'Brien referred to Kim as "Chairman Un," which is not how he's supposed to be acknowledged.

North Korea has reportedly been ramping up missile tests in the past few weeks, and promised to deliver a "Christmas gift" to the U.S. if denuclearization talks continued to stall. Christmas passed without any sign of a missile launch or attack, and O'Brien said Sunday that Kim may have reconsidered his threat. Still, "we always monitor the situation" because "Chairman Un has said that there would be something over Christmas," O'Brien said.

That's where O'Brien swapped Kim's family name for his given name — Chairman Kim would've been the right way of putting it. O'Brien may want a quick refresher on how Korean and other east Asian names work in case he ends up succeeding Secretary of State Mike Pompeo, who may step down to run for Senate in Kansas. Kathryn Krawczyk