In the realm of nuclear physics, a barn serves as a unit of measurement utilized to characterize the cross-sectional areas of reactions involving subatomic particles. The term was introduced by a group of physicists at Purdue University who were engaged in the clandestine endeavors of the Manhattan Project and required a covert-sounding unit equivalent to 10^−28 square meters. This area was deemed substantial for particle accelerators, prompting them to jest that hitting it would be “as easy as hitting the side of a barn”, thus giving rise to the term. The term barn has been in existence since at least the tenth century and is actually a combination of the Old English nouns bere, signifying “barley”, and ærn, denoting “place”; barley was a prevalent grain crop during the Anglo-Saxon era. Bere (also the root of the term barley if combined with the suffix -lic, denoting “like”) originates from Proto-Germanic baraz, also signifying “barley”, while ærn stems from Proto-Germanic razna, meaning “dwelling”.