Haggis, though considered purely Scottish could possibly have originated in the North of England.  It appears that the earliest known recipe/method is from the 15th century.  Just after a hunt, the offal was mixed with herbs, placed in the stomach lining of the (now dis-embowled) animal and cooked (a way of using parts of the animal that would otherwise have gone bad before being transported back to the manor house).  

However it is now prepared all over the world and consumed on all days of the year, not just [Burns Night][1].  Does using an [artificial casing][2] instead of an animals stomach change the flavor in any way?  Or is it necessary to obtain the stomach lining to make a traditional/authentic haggis?

  [1]: https://en.wikipedia.org/wiki/Burns_supper
  [2]: https://en.wikipedia.org/wiki/Casing_(sausage)