It all started with NYC's Flatiron Building...
The phrase 23 skidoo (sometimes 23 skiddoo) first appeared before World War I and became popular in the roaring twenties.
Perhaps the most widely known source of the expression derives from the area around the triangular-shaped Flatiron Building at Madison Square in New York City.
The building is located on 23rd Street at the intersection of Fifth Avenue and Broadway, and due to the complex geography of the intersection winds swirl around the building.
In the Roaring Twenties groups of men would gather to watch women walking by have their skirts blown up, revealing ankles which were seldom seen in public at that time.
Local constables, breaking up these groups of men, were said to be "giving them the 23 Skidoo".