Redshirt

Redshirt was a colloquialism amongst Starfleet personnel referring to expendable individuals who died in the line of duty. The term was derived from mid-23rd century Starfleet uniform, which featured bold red shirts for members of Starfleet security. Despite 24th century Starfleet security personnel wearing yellow uniforms the term continued to be used.

Vin Asunder had a pet tribble named Spike which he took with him on all away team missions believing it would bring him good luck and prevent him becoming a "redshirt". 

Real-world useage
The term redshirt is used extensively in the real world to refer to expendable characters, and has spread widely from it's origins of quickly killed supporting characters in episodes of Star Trek: The Original Series.

The notion of the redshirt is commonly parodied in other science fictions and comedies, and even in Star trek publications - the Star Trek: The Manga book Kakan ni Shinkou featured two short comic strips by David Reddick titled The Red Shirts which depicted the ironically comical mishaps of two red shirts (though because it was in the manga book they were depicted in black and white).