If you’re writing a novel, does that mean you can just make up whatever you want? Yes and no.
If you are writing a completely fictional world where you are creating everything, then yes. But the moment any aspect of the real world creeps in, then you’d better be careful.
Once any part of the real world enters your fictional world, you need to pay attention and get it right. If your story takes place in New York City, you cannot rearrange the streets or landmarks to suit your story. If you’re writing historical fiction, you cannot have an anachronisms peppering your world—no light switches, no telephones. (toilets, however were actually invented in the 1590s, although they didn’t catch on at the time. The first water closets began to be installed in the homes of the wealthy after 1778.) If you are writing about people with mental problems, you can’t just go with popular or stereotypical symptoms.
You most research whatever it is in your story that could have you called out for being inaccurate. If there is even one person who knows precisely when or where something happened, you need to ensure that person doesn’t shake their head and call you out for getting your facts wrong.
Aside from the fact that you’re going to annoy people and make them throw the book into the nearest garbage can, having accurate facts—and especially accurate jargon—will add to your credibility and a reader’s enjoyment of the book.
Now, if you deliberately get information wrong, I highly recommend putting in an author’s note (most likely before the start of the story because not all reader will go through to read it at the end). In your note, mentioned what you changed and what the accurate facts are. Readers will forgive a lot if you let them know that you do, actually, know what you’re talking about.
I was reminded of this while speaking to a licensed councilor who complained of an author having her teenage characters behave in appropriately for their age and mental abilities. I, myself, have read a book that was supposed to be set in Regency England but the author clearly hadn’t done a lick of research into the time period—getting clothing style entirely wrong, misusing noble titles and forms of address, and putting in a good number of anachronisms. I barely made it past the third page of the book before deleting it from my e-reader. When I confronted the author, who was someone I knew, she brushed off me complaints saying it didn’t matter.
Let me tell you, it does! So, please, I urge you, do your research before including something from the real world into your novel. You never know who is going to read it.
Oh, one other quick note on smeerps! A “smeerp” is a concept created by author James Blish who said that if you have a small, furry, long-eared animal, that hops around, and eats carrots, do not call it a smeerp just to make it sound exotic/alien/whatever. Just call the bloody thing a rabbit. If, however, you have a small, furry, long-eared animal that is planning on taking over the world and from there the entire cosmos, then do, go right ahead and call it smeerp.
A Smeerp