Old English wæg(e)n, of Germanic origin; related to Dutch wagen and German Wagen, also to way and weigh¹.

• wagon from Late Middle English:

  The Dutch word wagen is the source of our wagon. It is related to wain (Old English), an old word for ‘wagon’ that is now mainly encountered in the name of a star formation Charles's Wain, now more commonly called the Plough. Wainscot (Middle English) is from Middle Low German wagenschot, apparently from wagen ‘wagon’ and schot, probably meaning ‘partition’. If you are on the wagon you are avoiding alcohol. The original version of this expression was on the water wagon, which first appeared in America in the early 20th century. A water wagon was a sort of barrel on wheels which was used to water dusty streets. These vehicles had been around since the early 18th century at least, but it may have been the increasing popularity of the temperance movement in the latter part of the 19th century that gave rise to the phrase. See also hitch