Acre
A Dictionary of Law · Henry Campbell Black · 1891
A Dictionary of Law
A quantity of land containing 160 square rods of land, in whatever shape.
Serg. Land Laws Pa. 185; Cro. Eliz. 476, 665; 6 Coke, 67; Poph. 55; Co. Litt. 58.
Originally the word "acre" (acer, aker, or Sax. acer) was not used as a measure of land, or to signify any determinate quantity of land, but to denote any open ground, (latum quantumvis agrum,) wide champaign, or field; which is still the meaning of the German acker, derived probably from the same source, and is preserved in the names of some places in England, as Castle Acre, South Acre, etc.
Burrill.