Swearing doesn't just mean what we now understand by "dirty words". It is entwined, in social and linguistic history, with the other sort of swearing: vows and oaths. Consider for a moment the origins of almost any word we have for bad language – "profanity", "curses", "oaths" and "swearing" itself.
2013 June 14, Sam Leith, “Where the profound meets the profane”, in The Guardian Weekly, volume 189, number 1, page 37