A yo-yo is a toy made of two connected discs with a string wound around the axle between them. You loop the string around your finger, let the yo-yo drop, and it spins down and back up the string when you give it a slight tug. Simple yo-yos just go up and down, but skilled players can make them “sleep” at the bottom of the string, spinning in place, then snap back to their hand.

The yo-yo is one of the oldest toys in the world. Ancient Greeks played with similar toys over 2,500 years ago, and people in the Philippines developed versions that were later turned into the modern yo-yo. The modern yo-yo became wildly popular in America during the 1920s when a businessman named Pedro Flores started manufacturing them, followed by Donald Duncan, who helped turn the yo-yo into a household name.

The word also describes something that goes up and down repeatedly, like a yo-yo diet where someone's weight keeps rising and falling. If the stock market yo-yos, prices jump up and down unpredictably. When something yo-yos back and forth, it can't seem to settle in one place.

Yo-yo tricks have wonderful names: Walk the Dog, Around the World, Rock the Baby. Championship yo-yo players can perform dozens of complex tricks, making the spinning disc look almost magical as it flies through the air and lands precisely back on the string.