barn (n.) Look up barn at
Old English bereærn "barn," literally "barley house," from bere "barley" (see barley) + aern "house," metathesized from *rann, *rasn (cognates: Old Norse rann, Gothic razn "house," Old English rest "resting place;" sealtærn "saltworks").
Barley was not always the only crop grown as the data recovered at Bishopstone might suggest but it is always the most commonly represented, followed by wheat and then rye and oats. [C.J. Arnold, "An Archaeology of the Early Anglo-Saxon Kingdoms," 1988, p.36]
Another word for "barn" in Old English was beretun, "barley enclosure" (from tun "enclosure, house"), which accounts for the many Barton place names on the English map, and the common surname. Barn door used figuratively for "broad target" and "great size" since 1540s.