The history of swearing in movies goes back roughly as far as the history of sound in movies—once filmmakers learned how to make talkies, they made the characters in those talkies say any number of curse words. But that history also has a big gap in it: After filmmakers (and animators!) quickly embraced the joys of swearing in the early '30s, the Motion Picture Association of America put a swift end to the practice in film, banning swear words for a generation. (The famous "Frankly, my dear, I don't give a damn" in Gone With The Wind cost the film's producers a significant fine, though against its inflation-adjusted box office gross of $1.7 billion, they'd probably say it was worth it.) Those rules started to ease up again in the late '60s, and by 1970, a Hollywood movie—M*A*S*H—once again brought the word "fuck" to the masses.
All of that history is interesting to learn by reading, but to truly experience the visceral satisfaction of hearing bad words said aloud, turn your attention to this smart, informative video from the YouTube channel Movie Munchies, which traces the history of swearing in film from the first "damn" in 1929 to the first, er—well, see for yourself, in 1999's South Park: Bigger, Longer, Uncut. (NSFW, unless you're wearing headphones, obviously.)