What's the "een" in Halloween?
by 1970, U.S. military slang, from slang noun shortening of fragmentation grenade (1918). Related: Fragged; fragging.
Fragging is a macabre ritual of Vietnam in which American enlisted men attempt to murder their superiors. The word comes from the nickname for hand grenades, a weapon popular with enlisted men because the evidence is destroyed with the consummation of the crime. ["Saturday Review," Jan. 8, 1972]