Children had been playing with bamboo hoops in Australia for a long time. Since these hoops were made out of bamboo, they were not an indigenous invention by the aborigines, but as far as I know, nobody ever traced back the history of when bamboo hoop toys were first developed in Australia.
The hulu hoop toy was patented as a plastic toy in 1957, by Alexander Tolmer. His company, Tol-toys, sold 400,000 in Australia that year. It wasn't until the Southern California toy company Wham-O licensed the toy, that it took off like a rocket. Wham-O was not much larger than Tol-toys and Wham-O was to small to afford a Television advertising campaign. However, the president of Wham-O took some of the new hulu hoops and demonstrated them in elementary school playgrounds in the Los Angeles School district. This set off an enormous fad in 1958 that saw Wham-O sell more than four million hulu hoops in just four months. By 1958, the baby boom had reached critical mass and were a large enough cohort and old enough to cause such a stupendous fad. While Wham-O did not spend money on a national advertising campaign, the medium of Television soon picked up on the hulu hoop fad, spreading it nationwide.
Source: http://www.wham-o.com/history.html
If you scroll down past the three short videos showing Wham-O toy's blockbuster toys, there is some text. The fifth paragraph is devoted to the 1958 hulu hoop fad.