In 1919, after a shipment of wooden jumping sticks rotted en route from Germany to the US, George Hansburg patented and trademarked a metal version: the Pogo.
He introduced it to the chorus girls of the Ziegfeld Follies, who used the stick on stage. The ensuing Pogo fad of the 1920s even included a couple getting married on them.
But by 1921, pogo stick was being used generically, and pogo is no longer protected by trademark.
Photo: woodleywonderworks / flickr