Funny you should say that. In fact the word van is a contraction of caravan.
Caravan once used to refer to a large group of people carrying a lot of baggage and may have its origins in the Sanskrit word karabhah (meaning ‘camel’).
Why listen to me though? A Judge at the Court of Appeal has laid down some education on the matter.
(To be reasonable: van for most people nowadays does generally mean a motorised vehicle. I tend to use it over caravan mainly because it has fewer syllables – caravan is quite time-consuming. When I use ‘van meaning caravan I always prefix it with the apostrophe to denote the contraction.)