One of the mysteries of the English language finally explained.
1A cart, usually a barrel or tank on wheels, carrying water; specifically one used to water the streets by sprinkling water from small holes as it goes along; = water cart. Chiefly US in later use.
2Informal (originally US). In various expressions referring to abstinence from alcoholic drink, especially in "on the water wagon".
Mid 18th century; earliest use found in Daily Advertiser. From water + wagon.
water wagon/ˈwɔːtə ˌwaɡ(ə)n/
In this article we explore how to impress employers with a spot-on CV.