Assertion: racing's origin | /r/HasProperty | unclear
Facets:
Source sentences:
text: Late 1940s: The idea of side-by-side racing becomes known as “drag racing” – the origin of the term is unclear.
text: The definition of extreme sports is not exact and the origin of the terms is unclear, but it gained popularity in the 1990s when it was picked up by marketing companies to promote the X Games and when the Extreme Sports Channel and the Extreme Sports Company launched.