A pogo stick is a device for jumping off the ground in a standing position, through the aid of a spring.
They can be used as a toy, exercise equipment, or extreme sports instrument. It has had peaks and valleys in its popularity. It was very popular in the late 1960s and 70s, and is enjoying some renewed popularity now in extreme sports via the new sport of extreme pogo or "Xpogo".
It consists of a pole with a handle at the top and footrests near the bottom, and a spring located somewhere along the pole. The spring joins two sections of the pole, which extends below the footpads. It can be steered by shifting one's weight off the centerline of the spring in the desired horizontal direction thus producing horizontal locomotion.
A pogo stick that was not called a pogo stick was patented in 1891 by George H. Herrington of Wichita, Kansas "for leaping great distances and heights". This was an antecedent of the pogo stick as well as today's spring stilts.
We can call the pogo stick an eponym because the modern pogo stick name supposedly comes from a redesigned version that looks like the one we know by Hans Pohlig and Ernst Gottschall whose combined names give us "PoGo." They applied for a German patent in 1920 and described their device as a "spring end hopping stilt."