Murder Death Kill was a term coined in the 1993 action film Demolition Man. The term was used to describe a homicide. The film was set in an age where homicide was a very unusual thing, which is presumably why the term iterates the fact repeatedly.
Taken from the Demolition Man film:
"We can just wait for another code to go red. And when Phoenix performs another Murder Death Kill, we'll know exactly where to pounce."