O.E.
bereærn "barn," lit. "barley house," from
bere "barley" (see
barley) +
aern "house," metathesized from
*rann, *rasn (cf. O.N.
rann, Goth.
razn "house," O.E.
rest "resting place").
Barnstorming first applied 1815 to a theatrical troupe's performances in upstate N.Y. barns (usually featuring short action pieces to suit vulgar tastes); extended 1896 to electioneering, 1928 to itinerant airplane pilots who performed stunts at fairs and races.
Barn door figurative for "broad target" and "great size" since 1547.