One of the awkward things about writing is that we become acutely aware of some of the words we use, especially the ones we use most often. “Said” can make us physically cringe, even though readers often glaze over it. In the same way, saying the same character’s name over and over and over again can sometimes start to feel cluttered and over-saturated, and so we can be tempted to mix it up a bit.
Maybe if the protagonist’s first name is worn out, you’re tempting to switch to his whole name, or his surname. Maybe a nickname, or an identifier like “the bespectacled man”.
I know it’s tempting, but please don’t– or if you absolutely must, tread with caution.
What’s in a name?
Keep character names consistent. If you’re going to call a character James, have the same narrator call him James the entire time. Don’t keep switching between Jim, James, Jimmy and Mr. J. Bond. Every name you give a character– even if they’re different names for the same character– is yet another name the reader has to keep track of, and that can build up very quickly.
If a reader hasn’t picked up the book for a while, or isn’t familiar with the naming conventions of the culture you’re writing in, it’s easy to get mixed up and assume that the two names belong to different people. After all, it can be a bit of a leap for an outsider to realize that Dick is short for Richard, or that Sasha is short for Aleksander.
But if you’d rather go nameless…
When you’re using non-name identifiers– “the man in the tan jacket” or “the one who looked like neither a woman nor a man”, to borrow from Welcome to Night Vale and Lemony Snicket, respectively– try to stay consistent with that, too. These kind of names work best if the descriptor is unique in the story to that individual, and if it’s a particularly noticeable trait.
Of course, both of the writers I’ve mentioned are highly aware of that, and they like to play with those conventions. Snicket gives us “the man with a beard but no hair” and “the woman with hair but no beard”, while Night Vale gives us “the man who is not tall” and “the man who is not short”. These identifiers may be as vague as they come, but they’re used consistently throughout their respective stories. Moreover, the two halves of each pair are almost exclusively seen together and typically act as a single unit.
Look who’s talking
This isn’t to say that a person can’t go by other names. Your character’s drill sergeant might call her by her last name, her friends might call her by a nickname, and her coworkers might call her by her formal first name. If your story is told from multiple POVs, the different characters, each narrator might refer to the same character in a different way. But each POV should be consistent within itself, and it should always be clear who they’re talking about.
It’s also worth mentioning that names can change if they signify a radical shift in character. A character who survives a major trauma might start identifying themselves by a different name, to distance themselves from who they were before, as might a character going into deep cover. But in all of these cases, the deviation from the character’s typical name is deliberate and calculated, and in all those cases it means something.
And that’s what it comes down to: switching up a character’s names can be taxing on your reader, so if you’re going to put them through that effort, be sure to make it count.