Word Origin & History
O.E. æcer "tilled field, open land," from P.Gmc. *akraz "field, pasture" (cf. O.N. akr, O.Fris. ekkr, O.H.G. achar), from PIE *agros "field" (cf. L. ager "field, land," Gk. agros, Skt. ajras "plain, open country"). Originally in Eng. without reference to dimension; in late O.E. the amount of land
a yoke of oxen could plow in a day, afterward defined by statute to a piece 40 poles by 4, or an equivalent shape (5 Edw. I, 31 Edw. III, 24 Hen. VIII). Original sense retained in God's acre "churchyard." Related: Acreage (1859).