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)