wagon (n.)
"four-wheeled vehicle to carry heavy loads," late 15c., from Middle Dutch wagen, waghen, from Proto-Germanic *wagnaz (cognates: Old English wægn, Modern English wain, Old Saxon and Old High German wagan, Old Norse vagn, Old Frisian wein, German Wagen), from PIE *wogh-no-, suffixed form of root *wegh- "to carry, to move" (cognates: Sanskrit vahanam "vessel, ship," Greek okhos, Latin vehiculum, Old Church Slavonic vozŭ "carriage, chariot," Russian povozka, Lithuanian va žis "a small sledge," Old Irish fen, Welsh gwain "carriage, cart;" see weigh).

In Dutch and German, the general word for "a wheel vehicle;" English use is a result of contact through Flemish immigration, Dutch trade, or the Continental wars. It has largely displaced the native cognate, wain. Spelling preference varied randomly between -g- and -gg- from mid-18c., before American English settled on the etymological wagon, while waggon remained common in Great Britain. Wagon-train is attested from 1810. Phrase on the wagon "abstaining from alcohol" is 1904, originally on the water cart.