What Does "Katy Bar the Door" Mean?

Old Dominion's new song dropped today and it's so great!! Sexy and fun! In the song, there's a lyric I'd never heard before... "So Katy bar the door..." I took the liberty of looking it up for you, here's what I found -

1. The Modern Interpretation: “Katy bar the door” is a colorful colloquialism primarily found in the Southern United States. When someone drops this gem into conversation, they’re essentially saying, “Hold on tight, trouble’s brewing!”

2. The Origins:  The truth is, its exact origin remains a bit elusive. But this theory makes the most sense to me -

Catherine Douglas and the Scottish King: In 1437, Scottish King James I faced a mob attack in Perth. His room had a door missing its locking bar. Brave Catherine Douglas—let’s call her the original “Katy”—tried to save the day by using her arm to block the door. Unfortunately, her arm broke, and the mob did some nasty things to the king. From then on, she was known as Catherine Barlass. So, “Katy bar the door” could be a nod to her heroic (albeit painful) efforts.

3. The Moral of the Story:  “Katy bar the door” reminds us that trouble might be knocking. So, in Old Dominion's new song they're singing about coming home and making love to their partner like they're coming home from war... I think you can imagine the kind of trouble they're looking to stir up!!