wagon (n.)

"four-wheeled vehicle to carry heavy loads," late 15c., from Middle Dutch wagen, waghen, from Proto-Germanic *wagna- (source also of 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 go, move, transport in a vehicle" (source also of Latin vehiculum). It is thus related to way.

In Dutch and German, it is the general word for "a wheel vehicle;" its use in English 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., until 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 attested by 1904, originally on the water cart.

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Definitions of wagon from WordNet
wagon (n.)
any of various kinds of wheeled vehicles drawn by an animal or a tractor;
Synonyms: waggon
wagon (n.)
van used by police to transport prisoners;
Synonyms: police van / police wagon / paddy wagon / patrol wagon / black Maria
wagon (n.)
a child's four-wheeled toy cart sometimes used for coasting;
Synonyms: coaster wagon
wagon (n.)
a car that has a long body and rear door with space behind rear seat;
Synonyms: beach wagon / station wagon / estate car / beach waggon / station waggon / waggon
Wagon (n.)
a group of seven bright stars in the constellation Ursa Major;