Tracking down when a word originated is a fabulously slippery task.
Mad Men is being more careful about linguistic anachronisms than Downton Abbey. But is it really? And what about Deadwood?
The issue of anachronisms in period shows spills over to every aspect of the show. Much - one might imagine - to the shows' creators' dismay. I know of a fistful of blogs which obsessively track font choices in Mad Men, and which gleefully crow over fonts being used by the ad agency before they were invented in the real world.
(One unanswered question is, why should we care? It's a television show, not a history textbook. But this sort of question is its own answer to the sort of obsessive nerd who engages in this level of nitpickiness, myself included.)
Tracking down when a word originated is a fabulously slippery task. Text is usually considered the arbiter. But presumably a word has been kicking around in the world for a while before it ends up being entombed inside a book with a solid publication date. Except in cases where an author invented a word, most of the time they are simply recording a pre-existing world in print for all to see.
Of course, it's not as simple as "People didn't say that then." For example, the word "uppity" existed in the 1880s in America. Is its use in Britain in Downton Abbey an anachronism? The word had plenty of time to migrate across the Atlantic. But would it have? And even if it had, would it have been used by the character who said it?
I have a friend who found Deadwood unwatchable, because she was constantly distracted by all the modern swears being used. "C**ksucker" in particular drove her up the wall, because it wasn't invented until much later.
The show's producers have explained that they substituted modern swear words for the swears the cowboys would have actually used. Because what was a terrible swear word back in the 1800s (like "God's teeth!" or "God's truth!") barely even registers on our radar today. In other words, the producers felt it was more important for the characters' swearing to have the same impact as it would have at the time, than it was to be historically correct.
I suspect the same is true of Mad Men. Otherwise, the characters would spend a lot more time saying things like "shucks" and "aw, nuts" and "23 skiddoo!" and all those other wacky things people said in the 1960s which sound so quaint to us now.