The New Dictionary of Cultural Literacy, Third Edition. 2002.
deep-six
To dispose of, discard, or get rid of: “The board of directors deep-sixed the proposal without even reading it.” This phrase is derived from the noun “deep six,” meaning burial at sea and referring to the depth of water necessary for such a burial. The term was later used as slang for a grave (customarily six feet underground) and, by extension, as a verb meaning “to kill.”
