"Soup" could be made to stand for "SOUP On User's Player", where SOUP stands for "Soup Of Unordered Playlists".

As we often consider soup to be the raw ingredients of playlists, perhaps we should consider it as a "Soup Of Uncooked Playlists"?

Personally, I prefer real playlists, and think that abandoning them in favour of soups is a symptom of underdeveloped personality.