barn: n. [uncommon; prob. from the nuclear military] An unexpectedly large
quantity of something: a unit of measurement. “Why is /var/adm
taking up so much space?” “The logs have grown to several
barns.” The source of this is clear: when physicists were first
studying nuclear interactions, the probability was thought to be
proportional to the cross-sectional area of the nucleus (this probability
is still called the cross-section). Upon experimenting, they discovered
the interactions were far more probable than expected; the nuclei were
“as big as a barn”. The units for cross-sections were
christened Barns, (10-24
cm2) and the book containing cross-sections has
a picture of a barn on the cover.