as a land measure, was no certain quantity, but as much as an ox could gang over or cultivate. Also called a bovate. The Latin jugum was a similar term, which Varro defines “Quod juncti boves uno die exarare : Possunt.”
Eight oxgangs made a carucate. If an oxgang was as much as one ox could cultivate, its average would be about fifteen acres.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894