It's an ancient symbol representing the sun. It predates brown-shirted thugs by thousands of years. I've seen old printings of Kipling's works from the 1920s that have it stamped on the bindings, which is a bit jarring. But as I've said, it's a great deal older than that.
Prior to the 1930s, it was actually fairly common. It even wound up as the logo for an Vancouver-area women's hockey team[0].