Yo-yo
In its simplest form, a yo-yo consists of a pair of discs separated by a very short axle just wide enough to wrap a string around. The end of the string typically has a loop that is slipped over a finger, the other end of the string (attached to the axle) is wound around the yo-yo's "waist". When the yo-yo is released from the hand and falls, it has to spin to unwind the string, the two discs act as flywheels storing the angular momentum, and when the yo-yo reaches the limit of its travel, its spin makes it start to rewind the string back onto the axle in the other direction, making the yo-yo climb back up the string towards the hand.
With a suitable inflection of the hand, enough energy can be added to the yo-yo to compensate for frictional losses, so that the process can be repeated indefinitely.
Although images of people playing with yo-yos seem to be documented in artworks as far back as 440 BC, The yo-yo became a craze in the 1930s with the appearance of the improved "Flores" yo-yo, and again in the late C20th with further improvements in technology.
1928: Pedro Flores
Pedro Flores started The Yo-yo Manufacturing Company in 1928 with an improved version of the toy, which caught on so quickly that he had two more factories by the end of 1929. Flores sold the business on in 1932.
Flores' innovation was not to tie the string to the axle, but to incorporate a loop in the end of the string, so that when the yo-yo reached the end of its travel, it could continue spinning, stationary, within the loop ("sleeping"), until a tug on the string created sufficient pressure and friction with one side of the loop for the axle to "catch" on the loop of string, and start to wind back on the string and climb back up to the user's hand.
This looped slip string meant that the new Flores yo-yo could be used to carry out a variety of tricks and stunts that would bewilder onlookers only familiar with more traditional yo-yos.
Name
Previously known as a bandalore, the toy is supposed to have already been known as a yóyo in the Philippines (probably as an originless word expressing the toy's repetitive motion), and Flores, as an immigrant to the USA from the Phillippines, seems to have then been responsible for introducing the word to the wider audience.
