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[Uncle]

https://en.wikipedia.org/wiki/23_skidoo

Perhaps the most widely known story of the origin of the expression concerns 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, the latter two of which intersect at an acute angle. Because of the shape of the building, winds swirl around it. During the early 1900s, groups of men reportedly gathered to watch women walking by have their skirts blown up, revealing legs, which were seldom seen publicly at that time.