If Donald F. Duncan Sr. had been more vigilant, Yo-Yo Ma would have to change his name or pay cash every time he advertised a show. The enterprising Duncan trademarked the term “yo-yo” in 1932, even though the curious little toy had been around since at least 500 BC. Fortunately for classical cellists and enthusiasts of the quaint hobby, Duncan lost his trademark in 1965 when a court decided that the term had become generic. Not coincidentally, that was the year Duncan’s company went bankrupt. But the Duncan name had enough goodwill to hang on, even though the spinning discs are currently manufactured by the odd-sounding Flambeau Plastics Co. Today it is possible to be a “yo-yo champion” and member of the National Yo-Yo League. The jocks of Team YoYoJam help curator David Shayt deliver a lecture and demonstration, “Jamming With Yo-Yos,” during which yo-yos will be provided. Yay-yay! Shows start at 12:30 p.m., 2 p.m., and 3:30 p.m. in the National Museum of American History’s Flag Hall, 14th Street and Constitution Avenue NW. Free. (202) 357-2700. (Dave Nuttycombe)