deep-six, to

To abandon, reject, or otherwise get rid of. This slangy term dates from the mid-1900s and originated in the navy, where it meant throwing something or someone overboard. The “six” refers to the six-foot nautical fathom, the standard unit of measurement for sea depth. It soon was adopted into civilian language, as in an editorial about Massachusetts Governor Mitt Romney’s chances for national office: “I’d deep-six the joke [he tells] about the wily old farmer who pretends he’s feeding an alligator in order to scare some naked coeds out of a swimming hole” (Scot Lehigh, Boston Globe, March 11, 2005).