the.com/flatboat

means A long, flat-bottomed boat used to haul cargo or people down rivers, built simply because it only had to make the trip one way.

from A plain compound of 'flat' + 'boat' — the name doing exactly what it says. The design dates to early river trade in North America, especially on the Ohio and Mississippi, where builders needed cheap vessels to float goods downstream to market; once they arrived, the boats were often broken up and sold for lumber, since poling or rowing one back upstream wasn't worth the effort. The word itself is first recorded in American English in that riverboat-trade context, no older European ancestor needed — it's a homegrown term for a homegrown, one-way solution.