That would work for me too. I'm not keen on words like "Hey" and "Okay" in a medieval setting, but I've also found that I notice those most (and get annoyed by them the most) when I'm not fully immersed in the story.
I've caught myself writing "okay" a couple of times, and culled it, because it's a relatively recent phrase (mid 19th century). I never thought of "hey" as something strange, however. Something a person might say if someone bops them on the head, or shouts to get someone's attention.
Though I'm sure it probably has origins in the more recent past too.
That's where it gets strange. Some words are really quite old, but people think they're modern. And some words are fairly modern, yet almost no one thinks they're out of place, even in historical fiction.
I did
a blog entry on this a while back, where I tossed out some of those words that are older or newer than most people suppose.
Like when I'm referring to a prostitute, I doubt the common people (or any other, really) actually called them by that term. Therefore would it be off-putting to use "whore" or "hooker"? Another big problem is swearing. Would it be weird to use modern swear words, like (pardon my French) "fuck", "shit", or "dick"?
Whore was in use in Elizabethan times and is much older, I believe (or at least it's descended from a similar word that goes back a long ways). I've certainly seen the term used in medievalish fantasy too. Fuck and shit are quite old too, though of course usage has changed. Prick and pizzle wouldn't knock me out, but dick would. The use of dick to mean a penis is quite recent (mid 20th century), and anyway, does the man's name "Dick" even exist in your fantasy world?
The question comes down to translation. Is the culture in question likely to have equivalent words in their vocabulary, and if so, how are they likely to use them. As it turns out, the Romans spoke a different language than we do, yet they had words to describe sex acts, excrement, prostitutes, sexual anatomy and so on that were used very similarly to how we use them in the modern English-speaking world. Many of our modern swear words translate pretty well to their culture.
Conversely, medieval folks had some of the same words, yet they used many of them differently, and their most profane swear words were often religious in nature, not sexual or excretory.
A lot of our hangups about these words, and our aversion to sexual language and so on is more Victorian than medieval. Someone said in another thread that we're only just starting to "recover" from the Victorian era and develop a more historically normalized attitude about sex and so on.
And interesting thought. I'm no historian, but it does seem like our attitudes have evolved a lot in my own lifetime, though we've a long way to go (I mean, there are politicians who call oral contraceptives "whore pills," so...)