Acre
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
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. 5b.
Originally the word "acre" (acer, aker, or Sax. œccr) 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 reserved in the names of some places in Bng-and, as Castle Acre, South Acre, etc.
Burrill.