hash
n.— «I served as a boatswains mate aboard the USS Yorktown from 1964-68. We called our underwear “skivvies” and the hard to wash out parts on laundry day were called “hash marks” (After the stripes on uniform sleeves denoting time in service, which are also called this.)» —“Skivvies” by jackalope47 Wordorigins.org Nov. 2, 2002. (source: Double-Tongued Dictionary)
Further reading
Joe from Fort Lauderdale, Florida, asks about pony, the term he and his fellow maritime academy students used to mean “a practice test” or “a copy of a previous test” to help them crib for an exam. Among 19th-century British students, the slang term...
You know the expression fly in the ointment: It’s that glaring typo on an impressive resume or that first scratch on a brand-new car—the one little flaw that spoils it all. This phrase goes all the way back to the biblical Book of Ecclesiastes! And...