Yo-yo (yo-yo), also known as yo-yo and shake, is two spheres (not required to be round or of the same weight) connected by an axis (usually a screw, but also Wooden axis) is connected, and then the string is tied to the axis, and the other end of the thread is tied to the finger with a rope loop for play. When playing, use gravity or throwing force to break away from the yo-yo and start rotating. Then use the kinetic energy and friction of this rotation to wind the rope back into the yo-yo and back to your hand. If the yo-yo is rotated by other methods, such as motors, blade fans, etc., it will not be called a yo-yo by definition.

The first patent for the yo-yo toy was applied for by James L. Haven and Charles Hettrick in Ohio in 1866 in the United States. However, the patent for this yo-yo toy did not have any major impact. No apparent mass production. It was not until 1928 that a Filipino-American, Pedro Flores, opened the first yo-yo factory in California, USA. At the beginning, there were only a dozen people responsible for producing handmade wooden yo-yo toys. But within two years, he opened two factories in Los Angeles and Hollywood, employing a total of 600 employees and capable of producing 300,000 yo-yos every day.

Shortly thereafter, an entrepreneur named Donald F. Duncan discovered the potential commercial value of the yo-yo, so in 1932 he bought all the factories and products originally owned by Pedro Flores and started The door opened for Ken Yo-Yo. In the same year, the term yo-yo was registered as a trademark for the first time. At that time, Harvey Lowe won the world yo-yo championship in London, England.

Dangken’s first yo-yo was O-BOY, which originally seemed like a good investment. However, Dangken invested US$250,000 at the time, and the sales in the toy market were never satisfactory. The Donken Company lasted until 1946, and was lucky enough to open a yo-yo factory in Wisconsin. Since then, the town where the factory was located has been called the yo-yo capital of the world.

Until 1999, Donken's yo-yo was inducted into the American Toy Hall of Fame.