WHEN: 500 B.C. (2,500 years ago). It was named the Yo-yo in 1929.
WHO: Pedro Flores. It was later sold to Donald Duncan who added the slip string.
WHY: Versions of the yo-yo has been around for over 2,500 years. It became popular in the U.S. when Donald Duncan added improvements such as the sliding loop of string and the butterfly shape which allowed players to do tricks with the yo-yo.
FUN FACT: The yo-yo is considered the second oldest toy in the world. It was also the first toy in outer space.