It always makes me laugh when I see or hear language used that's supposed to represent vulgar language but without going the whole hog of actually using those words. Hence you get some interesting curse words, such as "sugar" or "bloomin" or "fup" - and you even have to use them on here, which is quite understandable, it being a family forum.
But when it comes to say a soap opera, it can be hilarious. I always think fondly of the euphemisms they used to conjour up on Brookside (a 'gritty' soap set in Liverpool); when they did a late night episode they 'let rip' with all the effing and jeffing they could, though.
Bill Bryson wrote about an article in one of the broadsheet newspapers which was trying to trace the first uses of certain swear words in the media. It managed to do so without ever actually printing said words.
So when Tolkien has Shagrat say of someone "the dung", I think we know what he
really means to say. Of course, Tolkien was not the sort of person we might expect to use swear words, so when representing those who use vulgar language he was quite limited in what he
could use.