Necro (pronounced Nekro) is from the greek/latin word for death. Merchant as in a person who sells. Put together, it means a seller of death. The first known use of this is in the Ten Minute Opera 'The Necromerchants Debt" written by Terrence Zdunich,
the creator of the cult classic 'Repo! The Genetic Opera'. The Necromerchants Debt was
the original inspiration for Repo! and some of it's songs became the basis for Repo! One such case would be with The Necromerchant's Debt song, Anno Domini (meaning year of the lord) turned into 21st century Cure. The character who sings both song is a Necromerchant or more commonly know as The Graverobber played by Terrence Zdunich in both cases.
My grandfather used to go to the graveyards and steal the clothes off
the corpses. He was a Necromerchant.
The local Necromerchant tried to sell me a Rolex. The exact one I saw
the deceased mafia head wear on
the day of his exacution.
The graverobber had a debt to pay to all those he had stolen from. He had a Necromerchant's Debt