
???
An entire language changes over the course of 2000 years, not just the slang. Two people from two millenia apart could hardly converse at all if you put them in the same room. The passage I presented from Karl E Wagner's essay already addressed this fallacy. It's quite obvius that when you're reading dialogue that takes place in a place that's on another plane of existence altogether that you're reading a translation, not a transcript. Yet, we feel fine seeing words like "hypnosis" and "mesmerism" in fantasy, even though in the context of the world there had never been a mythological character called Hypnos or Mesmer.
And the actual content of "how" people swear really doesn't change that much. I suspect you'd find that the references remain pretty similar: various taboo body parts, sexual acts, and excrement would be pretty much the basis just about anywhere.