Were they not allowed 1 swear word in each film to keep the same age rating in the US? Of course probably different for other languages, but I think this would be a good case to make use of it.
If we're talking Two Towers I want to save the f-bomb for when Aragorn tosses Gimli at Helms Deep. Gimli just roars "Fuuuuuuuuuuuuck!" as he flies through the air.