early 13c., "gallows," from Old French gibet "gallows; a bent stick, small stick with a cross" (13c.), diminutive of gibe "club; hoe," perhaps from Frankish *gibb "forked stick." "Originally synonymous with GALLOWS sb., but in later use signifying an upright post with projecting arm from which the bodies of criminals were hung in chains or irons after execution" [OED].
"to kill by hanging," 1590s, from gibbet (n.). Also "to hang a dead body in a public place for the sake of infamous exposure;" hence, figuratively "expose to ridicule" (1640s). Related: Gibbeted; gibbeting.