Chaplin
Better off silent
I suppose if I truly believed that the people in Deadwood spoke like the characters in the show it might help. Despite the claims of the show's producer I don't believe people spoke like that though.
http://www-csli.stanford.edu/~nunberg/deadwood.html
At the time, swearing wasn't actually anything except maybe rude to the Victorian people of the time (Alma Garrett). Otherwise, it was a perfectly normal thing.
Anyone can say "the occurance of the word **** didn't appear until 1920", because there was no documentation of the way people talked back then. You think Merrick is sitting in his newspaper office writing down how many times Swearengen uses the word ****sucker?
If nobody thinks to document something until a certain time, that doesn't mean it didn't exist before then.