A racial slur referring to people of East Asian descent, coined by US soldiers during the
Korean War. There are multiple proposed origins, but the most commonly accepted is that it if enemy Asian soldiers were shot
in the head with high-powered weapons, their heads would split as if they had been "unzipped". Another origin could be that when enemy soldiers were ran over by military Jeeps, there would be tire tracks on them that resembled zippers. It's violent origin makes it a
particularly derogatory pejorative.
It is often shortened to zip, though zip as a racial pejorative may have separate origins of its own