This topic has come up now and again, in posts about Gone with the Wind and more recently, Deadwood. It’s a technical and creative issue at the same time, and quite a tricky one, especially for people writing historical fiction or telling stories from the past on the screen.
The novelist has to find the balance between historical accuracy and the reader’s comfort level. There are extremes. On one end you might say that accuracy is everything, and damn the reader’s comfort; at the other, you might toss concerns about language accuracy out the window, and operate much in the way of Star Trek, where everybody understands everybody else, regardless of species or background, and nobody ever bothers to explain how that might be. Putting science fiction aside for a moment (although I keep meaning to write about language issues in Farscape, and will sometime) everybody has examples to share from novels and films that really stumble on language accuracy. Even really good writers mess up this way now and then; it’s almost impossible not to. Shakespeare had bells tolling in ancient Rome; Dorothy Dunnett once had her character Lymond proclaimed neurotic (in 17th century Scotland long before Freud was ever born). I read a novel (the title of which I’m blocking out) set in 15th century England where the main character tries to calm down a woman in distress by assuring her that the battle ahead of him is a piece of cake. In a comment to one of my posts about Deadwood, somebody pointed out that they used the word trenchmouth, which was coined in WWI.
The problem with lexical anachronisms is that they potentially destroy the fictive trance you work so hard to establish for your reader. It’s like ice water on the back of your neck on a hot day; you can’t not notice.
So how to avoid this mistake? One thing you can do is check idiomatic words and phrases for their place and time of origin. The Oxford English Dictionary is the usual place to do this, although it has some limitations. First, it’s too expensive for most people to own and even if you did invest, the hard-copy version is always out of date; second, it’s too expensive for most people to access on-line ($29.95 a month or $295 annually) unless you have library priviledges at a college or university that subscribes; third, (and most important) it’s limited to written language usage.
A word exists in the OED’s version of language history only once it has been written down. It should be clear that for most of the history of the English language, usage was not recorded anywhere at all, and so it’s hard to know when or where particular coins were actually used. On the other hand, the versatility and utterly amazing scope of the OED’s on-line search engine makes it useful in so many other ways, its limitations seem less important. You can, for example, search for whole phrases and idiomatic expressions. The next time I’ve got access to the on-line version, I’m going to see if they have the earliest citation recorded for ‘bald as an egg’ and while I’m at it, I’ll look up ‘piece of cake’ to see when it was first used, in writing, to mean ‘without problem or difficulty’ (I’m guessing it evolved from ‘easy as pie’ used in the same way). What I know for sure is, none of my characters, who inhabit the early 19th century, would have any idea what it means to say such a thing, and keep those words out of their mouths.
Of course, the more recent the setting of your story, the harder it becomes to check for origin and usage. I’ve got a steel sieve of a mind when it comes to remembering when certain phrases were in use. I know ‘cool’ was used when I was in high school, went out of vogue for a very long time, and then came back in, but I’d be afraid to put it in the mouth of a character in the year 1989 without checking, first. Slang associated with particular social groups has a very short shelf life, and can trip you up badly. There are dictionaries, of course, but they are out of date even before they are published, for the most part, and the OED can’t keep up with the incredible flexibility and creative power of spoken language.
There’s another, far stickier matter having to do with language anachronisms that I’ll look at (briefly) tomorrow.