I don't have much to say about the necropants, I simply had to mention them. A pair is on display at an Icelandic Musem of Witchcraft and Sorcery, where they are described as
The most popular object in the museum are the so-called necropants.
“Necropants are part of a complicated sorcery for gaining money,” Atlason explains. “The owner of necropants had to make a deal with a male friend while still alive about digging up his body after a natural cause of death, skinning it below the waste and wearing the skin as necropants.”
Atlason continues: “Then the necropants-owner would have to steal money from a poor widow and draw a magical symbol on a piece of parchment. After placing both in the necropants’ ‘pouch,’ the owner would magically come into possession of money.”
Original article, covering the museum in general
I suppose one could look to the tradition of the Hand of Glory for comparison. In pre-modern Europe, the severed hand of a condemned thief could be used as a magical item to make occupants of a house fall into a deep sleep, unlock doors, or otherwise make life easy for a burglar. Of course, the Nahuatl god Xipe Totec "The Flayed One" in Mesoamerica also comes to mind, though in that case a living victim was killed for/by flaying so that a priest could wear their skin for twenty days.
I suppose somewhat more on topic, this is yet another example of the increasing coverage of magical or otherwise "spooky" topics in museums and public attractions.