The legend is about a figure of Christ, a "Man of Sorrow" which is represented twice today.
In 1960 the original moved inside the Cathedral. On the outside you find a copy today.
wikipedia says about this Fixture on the outside walls,
"A figure of Christ ... affectionately known to the Viennese as "Christ with a Toothache", from the agonized expression of his face, various memorials from the time the area outside the cathedral was a cemetery and a recently-restored 15th century sundial, on a flying buttress at the southwest corner ... can be seen."
In the middle age it was a daily tradition to adorn such figures with fresh flowers. And it is fact that people used a piece of cloth to secure these flowers because it was and still is always windy around St.Stephens.