http://en.wikipedia.org/wiki/Skateboard

One proposed origin is that skateboards arose in the 1940s and 1950s, when children would participate in soapbox (car) races, using soap-boxes attached to wooden planks on rollerskate wheels. When the soap-box became detached from the plank, children would ride these primitive "skateboards".

Википедия, конечно, не самый highbrow источнег, но вот за что купила, за то продаю.