Chapter Text
We know that Jim Kirk is from Iowa, and Leonard McCoy is from Georgia, so both of them speak with American accents and phraseology. Using non-American word choices for these characters can jolt readers out of your story, which most writers would like to avoid.
Of course, in fan fiction, you can have them speak in any fashion you desire, but if you want to keep them in character, then there are some turns of phrase you might want to avoid.
Below are a few things that Americans typically DON'T say, unless they've been reading a lot of British novels lately. :-)
1. "Fringe" for the hair on Mr. Spock's forehead
We call those "bangs" in America. Yes, I know that "fringe" makes more sense. Yes, I know that "bangs" is a strange sort of word for the item in question. Still, if Kirk or McCoy notices that this part of Spock's hair is uncharacteristically messed up (or if they experience a desire to mess it up), they will think of his bangs, not his fringe. (And "bangs" is plural, so although his fringe is perfectly straight; his bangs are perfectly straight.)
2. "Fancy" meaning "like" or "desire" or "want" or "have a romantic crush on."
"Fancy" is almost never used as a verb in the US, and on the rare occasions when it is, it means "imagine." If you want Jim Kirk to have a desire for ice cream or shore leave (or Spock ;-D), then he wants ice cream or feels like ice cream. He might even have a hankering for ice cream (though McCoy might be even more likely to use this particular turn of phrase than Kirk would).
If they have a romantic desire for someone, then they like, love, have a crush on or are attracted to that person.
3. "Bit" for a section or part or piece of an object or task
Americans almost never say, "Let me finish this last bit" or "This bit is difficult" or "Hand over that bit." Where British people say bit, Americans usually say part or piece. Kirk will eat the last piece of pie. McCoy will finish the last part of his current task. Americans do say "a little bit" for "a small amount," but they rarely refer to individual parts or pieces of tangible objects as bits.
4. "You lot" for a group of people being addressed
If Kirk is sending one part of the landing party in one direction and another part in another direction, he won't address the people in one of the groups as you lot; he'd say you two (or you three, or however many there are) or you people or even just you. Since McCoy is from the South, he could say any of the things that Kirk might say; additionally, he might say you folks or y'all. (But make sure you don't use y'all for a single person; that "all'' is there for a reason, and the word is usually only addressed to more than one person. In some parts of the American South, y'all IS used for only one person, but this is an advanced skill that should be left to native Southerners. ;-D)
Similarly, if they are talking about a group to which their interlocutor belongs, Kirk and McCoy would not talk about your lot. If talking to Spock about Vulcans, for example, Kirk might say your people, or he might just say Vulcans, but he wouldn't say your lot.
5. "Jumper" for a warm garment worn on the upper body
In the US, a jumper is a sleeveless dress worn over another upper garment, such as a shirt; the article of clothing that is called a jumper in Britain is a sweater in the US. So Kirk is unlikely to change into a jumper when off duty, unless he enjoys cross-dressing in his spare time. He can wear sweaters, though. :-)
6. Irregular past tenses of verbs such as "learn," "smell," and "spoil"
Americans almost always use the regular past tense of such words. Kirk smelled a sickening honey-sweet odor in "Obsession," but he would never say he smelt it, nor would he have learnt what the cloud-creature smelled like; he'd have learned it.
7. "Whilst" is not a word over here; Americans say "while."
Jim was impatient while he was waiting for McCoy to tell him if Sulu would live. If he's impatient whilst he waits, he's had a personality transplant, and Scotty should go check the transporter right away. :-)
8. "Queue" is occasionally used as a noun in the US, but it's almost never used as a verb outside of computer science; Americans "line up" or "form a line" or "wait in line."
Jim's crew lined up to be transported down to the planet in "This Side of Paradise," but Kirk wouldn't have thought of them as queuing up.
9. Academic terms are quite different in each country.
While at Starfleet Academy, Jim Kirk would have studied for tests right before he took an exam; he would not have revised for tests before sitting an exam.
10. "Happy Christmas" is not used in the US.
Kirk and McCoy would say either "Merry Christmas," if they were speaking specifically of Christmas or "Happy Holidays," if they wanted to include the new year or other holidays, such as Hanukkah or Kwaanza.
11. "Sort" or "sort out" meaning "to solve a problem" or "to perform a task"
In the US, "sort" (as a verb) means "to assign objects to categories." Americans sort their laundry into darks and lights before washing, because if you wash everything together, it all comes out grey. :-) But if you have a problem in the US, you don't sort it, you solve it. If there are tasks to be done, you don't sort them, you do them, perform them, or take care of them. If a room is messy, an American will clean it or straighten it, but we would never sort it.
12. "Bum" and "Arse" as colloquial terms for "buttocks"
In the US, "bum" (as a noun) means "vagrant;" it is never used to mean "buttocks." If you want a colloquial term for buttocks, an American would say "butt" (more polite) or "ass" (less polite). If you want a politer or more childlike term, you could try "bottom" or "rear." Similarly, Americans don't say "arse;" it's "ass" in the US.
13. "Ruddy" as a mild expletive
In the US, "ruddy" is an infrequently used term meaning "of reddish complexion." Americans don't use it to express annoyance, so Jim would never say, "The ruddy warp core is overheating again." Mild expletives in the US would be "darned" or "dratted;" slightly stronger would be "damned."
14. Many uses of "rubbish"
Americans never say that they're "rubbish at" something. We're bad at it, we suck at it, we're horrible at it, but while we understand what you mean when you say you're "rubbish at" something, it's not something an American would say.
If you say something we think is ridiculous, we won't respond with "Rubbish!" In formal situations, we'd say "Nonsense," and in casual situations, we'd say, "Bullshit," but we'd never dismiss something someone else said with "Rubbish." "Garbage," perhaps, but not "rubbish."
15. "Bollocks" in any usage
Most Americans aren't even sure what this word means. :-) The word over here is "balls."
16. "Knickers" for women's underwear
Knickers are short trousers in the US, a garment that mostly stopped being worn around a century ago. Women's underpants are either called "panties" or "underwear," never "knickers." Kirk would never think about "getting into her knickers," though he might think about "getting into her pants." And McCoy might remove a lady's panties or underwear while making love to her, but he'd never take off her knickers.
17. "Mum" for a person's mother
The word is "mom" in the US. Kirk and McCoy might wonder what kind of mom Rand or Uhura or Chapel would make, but "mum" is a rarely used word meaning "silent," found mostly in the phrase "keeping mum."
18. "Chap" for a male humanoid
Americans just don't say this. We say "man" when speaking relatively formally and "guy" when speaking colloquially. Younger Americans use "dude" in addition to "guy" as a colloquial term for male humanoids. "Dude" wasn't a word that anyone would have put into Kirk's mouth in 1966, and to me it sounds more like something reboot Kirk would say than something TOS Kirk would say. But it is reliably American. :-)
19. "Spanner" for a tool to loosen or tighten things.
We call that a "wrench" in the US. McCoy is unlikely to use one in the course of his normal duties, though in an emergency, he could possibly pick one up to use as a weapon. Kirk, on the other hand, could use one for that purpose or could help out in engineering for some reason. So Scotty could pick up a spanner and hand it to Kirk, at which point it will become a wrench. :-)
20. There are lots of other words that don't exist over here. I find most of them quite charming when I run across them in British novels or when an English friend says them, but they're words that Kirk and McCoy wouldn't say and might not even know.
These words include knackered, barking (for "crazy"), chuffed, witter, and lots more. If you're writing a story and aren't sure if something is said in the US, feel free to send me an e-mail or to leave a comment here.
Of course, you could assume that the language will be more homogenized in the 23rd century than it is now, and words that are almost never used by Americans today will be so used two centuries from now. But your readers live now, and their reactions to words are those of the present century, so it is still the case that using words in a way that Kirk and McCoy didn't use them in TOS can jolt readers out of your story. You can do that if you want — heck, in fan fiction, you can do ANYTHING you want — but this little list is intended for those who do want to make Kirk and McCoy speak in their usual fashion.