Analysis / Red Shirt

So, why is it "redshirt"? Why red? why a shirt? Because of this:

Red was the color of shirt worn by the nameless security personnel on the original Star Trek series. Their only job was to get eaten, shot, stabbed, disrupted, temporally-shifted, frozen, desalinated, or crushed into a cube (except for Scotty, being the Chief Engineer). Their death would give William Shatner and DeForest Kelley a corpse to emote over, and Leonard Nimoy a corpse to, well, not emote over. (Gene Roddenberry inverted this trope in Star Trek: The Next Generation when he had all officers of command rank wear red shirts while the security and engineering departments wear gold - but as you can see, the theory is the same even if the colour isn't.)
http://tvtropes.org/pmwiki/pmwiki.php/Analysis/RedShirt