<P> James fled into a sewer tunnel as the queen and her ladies quickly replaced the floorboards to hide his location . Catherine sprang to the door and placed her arm through the staples to bar the assassins' entrance . However, they forced the door open anyway, breaking Catherine's arm, and discovered and killed the King . From that point on, according to the story, Catherine took the surname of "Barlass". </P> <P> The idiomatic phrase "Katy, bar the door!" (a warning of the approach of trouble) may have its origins in the story of Catherine Douglas . Dante Gabriel Rossetti recounted the story of Catherine Douglas in verse in 1881, under the title "The King's Tragedy". This poem contains the line "Catherine, keep the door!" </P>

Where did the saying katie bar the door originate