Did you know that Dwayne "The Rock" Johnson got a tank named after him? The actor/wrestler/producer took joy in being given the honors and posted the image onto his social media. Because you can't go two days on the internet without some sort of backlash from people with nothing better to do than argue over some mundane thing that has absolutely no bearing on their life... people argued.
On one side, some people are upset that he felt honored for it because, you know, that has to mean he is advocating war or whatever. Counter-arguers are also quick to jump at the chance to point out that it is a high honor for such a beloved figure because he's always been a friend and supporter to the military and veteran community.
In reality, the process of naming tanks, artillery guns, and rocket launcher systems isn't as grandiose as the people arguing are making it out to be.
When it's time for a crew to take command of a new vehicle, they need to give it a name.
With some exception, you name it entirely for the purpose of easily identifying it. When you're walking through the motor pool, reading the name stenciled on the gun or rocket pod is going to be a lot easier to read from a distance than its serial number.
Unlike with Humvees or other troop carrying military vehicles often forgotten until it's time to use them, artillerymen and tankers take pride in what is theirs. The name has to be something that the crew could proudly sit in for hours until the FDC finally gets around to approving a fire mission.
The name itself is generally something that invokes strength, humor, or holds sentimental value to one member of the crew - like a loved one. The command staff usually doesn't bother as long as it isn't (too) profane and it typically follows the guideline of the first letter being the same as your company/battery/squadron for uniformity.
So an MLRS in Alpha Battery could be named "Alexander the Great" or "Ass Blaster." Bravo Battery gets something along the lines of "Betty White" or "Boomstick." Charlie gets names along the lines of "Come Get Some" or "Cat Scratch Fever." And so on.
As for the tank named "Dwayne 'The Rock' Johnson," well, just happens to be in a Delta Squadron, the crew were probably fans of his work, and his name invokes strength. I can attest, entirely anecdotally of course, that Dwayne Johnson isn't that uncommon of a name within Delta Batteries/Squadrons.
The crew comes up with the name, submits it to the chain of command, and if it gets approved, they spray paint the name prominently on the gun. If the commander wants it to be all people's names, then they're all people's names. If they give the troops free rein, then that's their prerogative.
It should also be noted that some commanders may forgo the entire process of naming their military vehicles and guns altogether. It is what it is, but some tankers and artillerymen may see it as bad luck to not give their baby a name and troops can be particularly superstitious. That, or they may just be saying it so they can spray-paint "Ass Blaster" on their tank's gun.