A yo-yo (also spelled yoyo) is a toy consisting of an axle connected to two disks, and a string looped around the axle, similar to a spool. It is an ancient toy with proof of existence since 440 BC. The yo-yo was also called a bandalore in the 17th century. It is played by holding the free end of the string known as the handle (by inserting one finger—usually the middle or ring finger—into a slip knot), allowing gravity (or the force of a throw and gravity) to spin the yo-yo and unwind the string (similar to how a pullstring works).
https://en.wikipedia.org/wiki/Yo-yo