"front part of an army or other advancing group," c. 1600, shortening of vanguard.
van n.2
"covered truck or wagon," 1829, shortening of caravan. Century Dictionary suggests this was perhaps regarded as *carry-van.
Entries linking to van
vanguard n.
mid-15c., vaunt garde, from an Anglo-French variant of Old French avant-garde, from avant "in front" (see avant) + garde "guard" (see guard (n.)). Communist revolutionary sense is recorded from 1928.
caravan n.
1590s, in reference to in North Africa or western Asia, "company of travelers, pilgrims, merchants, etc., going together for security," from French caravane, from Old French carvane, carevane "caravan" (13c.), or Medieval Latin caravana, words picked up during the Crusades, via Arabic qairawan from Persian karwan "group of desert travelers" (which Klein connects to Sanskrit karabhah "camel").
Used in English for "any large number of persons traveling together with much baggage" (1660s), hence "a large covered carriage for conveying passengers" (1670s) or later for traveling shows or used as a house by Gypsies. In modern British use (from 1930s), often a rough equivalent of the U.S. camper or recreational vehicle.