Whether it’s “Rocket Man” or “Tiny Dancer,” you may want to think twice about nicknames at work.

President Trump’s latest nickname for a rival is “Rocket Man,” a kiss-off to despotic North Korean leader Kim Jong Un and his nuclear-program ambitions. Trump debuted the Elton John-inspired nickname Sunday on Twitter, and proceeded to drop it again during his first, wide-ranging speech to the United Nations two days later. (“Rocket Man is on a suicide mission for himself, and for his regime,” he said.)

“Rocket Man” was not a one-off: The nicknamer-in-chief has a storied history of doling out unsolicited designations (looking at you, “Low Energy Jeb” Bush, “Lyin’ Ted” Cruz and “Crooked Hillary” Clinton). So what are the pros and cons of nicknames in the workplace, and what’s the best way to shake an unwelcome one? We asked some experts.

“A nickname implies some informality; it implies some social interaction above and beyond a simple professional relationship. It can be a positive in that context,” John L. Cotton, a professor of management at Marquette University, told Moneyish. But “it can also come across as a negative if it’s seen as being too casual in a more formal kind of environment, especially with people who maybe you don’t have a relationship with.”

The audience, setting and relationship between the nickname giver and recipient matter, Monster.com career expert Vicki Salemi told Moneyish. While nicknames among peers below management may be fine, subordinates nicknaming the boss “is definitely not encouraged” because it may seem like a sign of disrespect. Bosses, meanwhile, have more leeway — but should make sure nicknames are PC, avoid playing favorites by singling out one person for a nickname, and steer clear during meetings.

“And bosses shouldn’t give nicknames to other bosses; the higher up the ladder you go, the more it’s a no-no,” she said. “It would be really unprofessional and inappropriate, for instance, on a quarterly earnings call, for the CFO to indicate one of their peers as Juggernaut, Kung Fu Panda or Moneybags.”

Indeed, bosses especially should “tread very carefully” in assigning nicknames, Kelly Williams Brown, an author who has reported extensively on etiquette and workplace dynamics, told Moneyish. “A nickname can be both used to establish closeness or friendship, or it can be used as a power dynamic,” she said. Managers typically “can build camaraderie (in) other ways,” Salemi added.

It’s inappropriate for managers to “take it on themselves to presume that they can rename people” — at least when that nickname is “based not on a strength but on a weakness,” executive coach Roy Cohen told Moneyish. But acceptable nicknames for subordinates might include a name by which they prefer to be called or a compliment: “For example, ‘Champ,’” Cohen said. “What does that imply? It implies that you are good at what you do; you’re successful.”

If you find yourself saddled with an undesired or offensive nickname, it’s best to “nip it in the bud as soon as possible,” Brown said, since nicknames can stick fast. “You can do that by just saying, ‘You know what? Actually, I prefer Kelly.’” Use a neutral, positive tone that doesn’t sound angry or accusing. “You do not want it to be known that this riled you or annoyed you,” she said. “And you don’t want to seem like you don’t get the joke, because then it becomes a lot funnier to the people telling the joke.”

You’re also entitled to ask the boss to lay off, Salemi said. “You do have a right to be assertive.” Take her aside and politely say you’d prefer she used your actual name going forward: “They should respect that, and if they don’t, then that’s a bigger issue going on at your office,” Salemi said.

Ultimately, Cotton said, “it’s a matter of letting people know you don’t like it. And if they’ve got any consideration at all, they will back away.” If you’re uncomfortable working in an environment that encourages throwing around mean or belittling nicknames, he added, “get out of it.” “If you’re not comfortable with that, you’re probably not going to fit in and you’re probably not going to be very successful.”

With that said, a good nickname makes you easily memorable, Salemi said. It can humanize, soften and connect you to your coworkers, Cohen added, particularly if others see you as rigid or aloof. “If it’s a positive nickname, if it evokes success, if it conveys that you’re well liked, then I’d say it’s great,” he said. “If it’s something that feels comfortable and natural for you, absolutely.”

When picking a nickname for yourself or deciding to let one stick, Salemi said, keep in mind that “your nickname is part of your professional brand — so it’s important, if you have one, to choose accordingly.” “If someone introduced the CEO to you, would you feel embarrassed or proud by that nickname?” she said.