The Legend of Kate Barlass
On February of 1437, King James I was assassinated by a band of murderers while on a visit to Perth. His chamber door had metal straps for a wooden bar, but the Chamberlain had taken up the bar. One of the Queen's ladies-in-waiting, heroically placed her bare arm in the straps to try to save the King. The murderers forced through the door, broke her arm and killed the King.
Her descendants to this day bear the broken arm on their family crest. Her name was Kate Barlass, and she is the source of the phrase, "Katy Bar® the Door".