It means approximately "the original problem", i.e. where the problem ultimately stems from. The prefix "ur" is derived from old high German "ur", old Nordic

It means approximately "the original problem", i.e. where the problem ultimately stems from. The prefix "ur" is derived from old high German "ur", old Nordic "ōr" or Gothic "us": "from, out of". That there's an ancient city of that name is purely incidental.