A
redshirt is any character or person in a work of fiction who is meant to serve only as cannon fodder, and dies soon after being introduced. The term stems from the popular American
science fiction television series
Star Trek. In these series, characters wear shirt colours defining their station and/or area of expertise. In the original 1966 series, a person wearing a red shirt was a member of the Engineering or Security department on any
Starfleet vessel. Security officers had a habit of meeting tragic and fatal ends (with at least one dying nearly every episode), and fans of the series have come to use the term "redshirt" to describe any nameless, faceless, and--most importantly--expendable character.
In later Star Trek series, red shirts came to be worn by members of the Bridge crew instead.
A redshirt is a player on a college sports team in the U.S. who has been kept out of competition for a year in order to prolong his or her eligibility.