prettygoodword

barn (BAHRN) - n., (nuclear physics) a unit of nuclear cross section, equal to 10⁻²⁴ square centimeters.

One last odd unit of measure, this a new one. For the etymology, I'll let Wikipedia take over:

During Manhattan Project research on the atomic bomb during World War II, American physicists at Purdue University needed a secretive name for a unit with which to quantify the cross-sectional area presented by the typical nucleus (~10⁻²⁸ m²) and decided on "barn". They considered this a large target for particle accelerators that needed to have direct strikes on nuclei, and the proposers, physicists Marshall Holloway and Richard Baker, said that the constant "for nuclear purposes was really as big as a barn". In the American idiom "couldn't hit the broad side of a barn" refers to someone whose aim is very bad. Initially they hoped the name would obscure any reference to the study of nuclear structure; eventually, the word became a standard unit in nuclear and particle physics.

Same article notes that Manhattan Project folks also coined the unit of time called a shake, equal to 10⁻⁸ seconds.

---L.