I’m uncertain how difficult such a tool would be, but I had an idea for a writing tool that would serve as an anachronistic language detector. The user would insert text, select a year, and the program would return the text with any words highlighted that hadn’t yet appeared in written English. This way, you could avoid any anachronistic language in historical language. Say you’re writing a story set during the American Civil War. You might have one character call another a “moron,” without realizing that that word first occurred in written English in 1910, and was initially a clinical term for someone with an IQ between 50 and 70. The word itself seems timeless, though, at least to me. I wouldn’t think twice about seeing it in another century. But if you wanted true historical accuracy in your writing, it’d be useful to know when it first appeared without having to look up every word in your dialogue manually.
You’d probably have to set up some sort of look-up against the Oxford English Dictionary, searching for the earliest use of a word. And of course, it wouldn’t catch differences in context, either. But I think it’d be a neat little program to be able to use. Improvements might include indicating the year in which the anachronistic word first appeared, and maybe even recommending synonyms that actually did exist at the time. I wish I knew more about programming so I could try to create something like this myself.