Crapper story is true. To this day (well, at least 'til the late 1960s) there was a "Thomas Crapper & Sons" plumbers in the UK (a random memory from an ancient Road & Track magazine "Ampersand" back page photo).
Not convinced about the true context for the paper bag...
As an aside... remember the old SNL sketch about the cocktail party featuring The Earl of Sandwich and other eponymous English nobles, some rather fanciful (e.g., Lord and Lady Douche-Bagg)?