Katy bar the door is an exclamation that means watch out, trouble is on its way. It is an American phrase, usually heard in the southern United States. The exact origin is unknown. One possible source of the phrase Katy bar the door is a Scottish ballad called Get Up and Bar the Door published in 1776. Another possible source is the story of Catherine Douglas, the woman who sheltered the Scottish King James I from an unruly mob in 1437. As the story goes, Catherine Douglas and James I were hiding behind a door that didn’t have a lock. Catherine attempted to bar the door with her arm, but the crowd broke through and murdered the king. Interestingly, both of these stories concerning this American phrase have a Scottish origin, demonstrating the influence of the many thousands of Scottish immigrants to America in the eighteenth and nineteenth centuries. Katy bar the door is sometimes spelled as Katie bar the door.
“Our concern is that they’re going to do whatever they have to do between now and November to get through that election, and then ‘Katy, bar the door!’ after that,” Klarides said. (The Hartford Courant)
“If they don’t get some kind of responsible oversight, it’ll be ‘Katy bar the door,’ and they can do anything they want to,” he said. (The Des Moines Register)
Folksy language: You know you’re somewhere when people say, “Katy, bar the door!” in the middle of a conversation. (The Atlantic Magazine)
“But if something happens with these emails or she stumbles in Iowa, then it’s ‘Katy, bar the door.’ ” (The New York Times)
‘If it breaks out, it’s literally, “Katie bar the door”,’ Gen John Kelly told said during a public discussion at the National Defense University. ‘And there will be mass migration into the United States.’ (The Daily Mail)