One of my favorite parts of worldbuilding is developing dialogue and speech patterns. Thanks to the Internet and the connectivity it creates, you don’t have to be an actual philologist like Tolkien to create realistic jargon, slang, and colloquialisms in your speculative fiction.
In creating new worlds, fitting dialogue helps to render the setting and make it feel real. I love writing dialogue in general, but I particularly like making my characters talk like they live in the worlds they inhabit. One thing that helps dialogue feel more natural is developing an understanding of what these three things are, and in your own world, understanding how and why the terms are used in a slightly more technical way than we do in our world.
As an example, with jargon, all those military terms, cop terms, and medical terms everyone loves to mimic from television shows and movies are specific to those professions. Standing in a kill box, or requesting a sitrep, or asking for something, stat are all particular to those respective fields. Jargon, however, does not exist to sound cool (although that is what many people on the fringe of or outside of the profession might use it for). Jargon exists to convey an otherwise more complicated idea in a manageable amount of time. Often, even in the individual fields, the original meaning of the word or acronym is lost to the new, idea the term now represents.
As an example, a kill box is defined by Definitions.net as “a three-dimensional target area, defined to facilitate the integration of coordinated joint weapons fire. It is a joint forces coordination measure enabling air assets to engage surface targets without needing further coordination with commanders and without terminal attack control.” Here, the idea is a very specific one that has implications even beyond the commonplace understanding that if you stand there you will get wrecked.
If we look at how jargon functions in our own world, it can help us create jargon for imagined worlds. What are the complicated ideas in your world that would take a professional in that world too long to spell out, but a colleague would understand the idea without explication?
In Dusk, Earth has achieved space-faring tech. A pilot would say a ship that was in an uncontrolled barrel roll has lost its y-axis or lost its y. A common citizen speaking casually might say someone who was manic or irrationally upset flipped his y. The technical term includes the idea that in space, vehicles are not always traveling on the same plane, but the front, back, top, and, bottom of a vehicle are always aligned on the y-axis passing through it the same way. The jargon carries the implication that whether you were in space or planetside, both an observer or the pilot of the craft would agree that a barrel roll was the same thing, whereas the commonplace perception just means ‘out of control.’
The important thing here is not so much to be able to write out a definition like the kill box entry about all your invented jargon but to think about what the professionals in your society would need to say quickly. Do you have an idea about the way healing or medicine works in your world? Does it make sense for a wizard or a doctor or a faith healer to spell out what is happening every time, or would they have a term as a placeholder for the idea? How would this then translate to how people within the society speak? If the society is at war, or they revere their healers as demigods, or they are afraid of the law enforcement, the common people might also adopt the jargon in a less specific manner as slang.
Slang works in very much the same way as jargon but is specific to a group of people in a society rather than a profession. It may not seem like the same because of the often negative social connotations, but let’s look at how slang is used.
In David Simon’s The Wire, the drug dealers, often the younger ones, refer to the Baltimore narcotics cops as knockos. This term is not only very specific (because it implies specifically narcotics officers that raid stash-houses and corners or who may be undercover), but there is often discussion on the Internet on the term being a specific Baltimore inflection–the ‘knock’ part, however, makes sense as you see them knocking down doors and handling the corner boys roughly.
An invented terminology should not only be specific to an area or group, but without creating confusion for the reader, should say something about the characters or their society. With knocko, it shows not only a level of belligerence but also of respect. One thing to keep in mind is that slang carries the attitudes of the society with it in a way that jargon may not. For instance, a weapon in speculative fiction might carry a positive slang name in a violent society but an extremely negative one in a pacifist society–especially if the establishment has an opposing view.
A colloquialism is slightly different than slang in that it is more widely used and often less indicative of social values. Informal but less localized language is used quite commonly in reality, but can be a bit trickier when creating your own. Calling someone a clown likely just means he can’t be taken seriously but does not necessarily reflect how the society feels about clowns, but calling someone a trash-monkey in a town overrun by monkeys says something both about how the speaker feels about the subject, and how the speaker feels about monkeys, which have a direct effect on that setting and is closer to slang.
Sometimes, this can be dealt with by using more common contemporary colloquialisms (like wanna, dunno, and what the heck) and replacing less common ones (like carjacker) with ideas specific to your world (like levboost in a world with levitating cars). When the world’s scale is larger, the difference between these three can get hazy, but they can still help bring realism to the worldbuilding without stressing over proper linguistic terminology. At the end of the day, you don’t have to properly categorize the term for it to work well in your narrative, but understanding how and why it works might help it feel more real and read more smoothly.
There are also many people out there who caution against heavy or even casual use of jargon, slang, and colloquialisms in fiction, and they make very valid points. You want your characters to feel like real people when they talk, but you have to balance that with confusing the reader out of the narrative or making your dialogue feel stilted. It may help to read aloud–especially to another person–and gauge his or her reactions and your own. In the end, telling a story should be the ultimate goal, and the richness of the world and the characters’ language should help make the narrative more accessible and fun or interesting without being overly difficult to read through.