DEMONREAPERCHILD, THIS IS J.LO. J.LO, DEMONREAPERCHILD.

Right decision, Jennifer Lopez, wrong reason.

The actress and pop star said Jan. 2 that she no longer wants to be called “J.Lo,” the nickname she foisted on the world in late 2000 alongside then-boyfriend Sean Combs, who similarly wanted to changed his name to “P. Diddy” from “Puff Daddy.”

Now, according to the World Entertainment News Network, Lopez is sick of the nickname and calling it “just a bit of fun that got out of hand,” even stressing to the world that J.Lo “is not a real person.” Her next album is called “Rebirth,” but was once to be “Call Me Jennifer,” both her way “of saying goodbye to the whole J.Lo thing.”

The problem was in taking on the name in the first place. It’s okay for bands to take on a group name, especially for ones such as the Polyphonic Spree, which has more than two dozen members, but a bit cheesy for a single performer who’s already a star. Nicknames evolve. They’re not to be requested. (Mariah Carey wants to be called Mimi, but she claims friends and family really call her that.)

Many nicknames aren’t even wanted. Mel Torme is said to have disliked being referred to as “The Velvet Fog,” and Bruce Springsteen supposedly resists being “The Boss.” But of self-selected names, only Prince is memorable for abandonment. The unpronounceable glyph he took on, causing many to instead call him The Artist Formerly Known as Prince, was intended to be an irritant to the record company he felt was screwing him, and when the contract ended, so did the name.

Combs hasn’t taken back P. Diddy. Christina Aguilera hasn’t taken back Xtina, the little-used name she gave her, um, dark side.

But Lopez should be congratulated for taking the step, even though it was obviously a reaction to a year’s worth of public relations nightmare that damned her as imperious, grasping and awful. Gossip said she was so keen on the trappings of wealth and celebrity that Ben Affleck found their life together distasteful, leading to the end of their romance. She was ratted out as a bitch and a diva, resulting in diminished interest from consumers. Her movies performed badly — remember “Gigli”? — and critics said she did, too, causing her to announce a retreat from Hollywood. (Whether the announcement means anything is a separate issue.)

She should have ditched “J.Lo” because it was stupid. Adults do not run around changing their name every few years and demand that others play along.

This becomes more obvious in looking at, of all things, the 26-house fire set Dec. 6 in Maryland’s Charles County. The investigation goes on, but police have arrested several men in their early 20s who call themselves The Unseen Cavaliers (after the car), hang around at the local fast-food joint — but at a distance, in a kind of we’re-here-but-we’re-not-with-you pose — or listen to heavy metal and play video games.

As part of this gaming and faux gang world, these shiftless, low-income lost boys call themselves such names as CrashCourse, CrashBlade, WebPhantom and demonreaperchild. These are boastful names of violence, sharpness, mystery and danger adopted by guys who, to their credit, are accused of one of the biggest arsons in history, but generally are the sort who hang out in front of minimarts and sort change to pay for giant Mountain Dews.

The dull reality of unmet ambitions makes the fantasy world of nicknames reasonable, just as it’s good for children to exercise rich imaginations. But for a beautiful movie star and singer with annual earning power in the millions and a life of privilege and acclaim ... well, “J.Lo” was a little silly and sad.

Lopez is better off without it, if only as an example to others.