"By the close of the decade [the 1930's], things were on the upswing economically and the country splurged on the New York World's Fair and the San Francisco Fair simultaneously, both of which offered a glimpse of the World of tomorrow. Television was first seen by the mass public, the Trylon and Perisphere dominated the skyline in New York's Flushing Meadows Park, and the giant red National Cash Register totaled the number of daily visitors, in the window where the dollars and cents usually appeared. The curious from all over the country, as well as from abroad, swarmed in. A funny cockney dance, the Lambeth Walk, became a fad as couples slapped their thighs, walked side by side, hooked one another's arm, then separated to toss a clenched fist over the right shoulder with an extended thumb while saying "Oy!"
According to webref.org:
The Lambeth Walk is a walking dance done in a jaunty, strutting fashion. It was originally an old English step performed in the Limehouse district of London and danced to the song "Doing the Lambeth Walk." This dance was introduced into the United States about 1937.
There is also some info on streetswing, including a description of the step patterns.