Well, I was about to give up, but then I stumbled upon this Japanese fansite:
http://www.dbmania.net/db-names.htm
「プンター→地名orタプン(擬音)」
"Puntā → chimei or tapun (gion)"
"Puntā → place name or tapun (onomatopoeia)"
According to this, it was either named after a place (there are quite a few places called Punta in the world like the Punta Cana in the Dominican Republic) or it's an anagram of the Japanese onomatopoeia タプン (tapun), which is used for something full of liquid:
https://ja.hinative.com/questions/23546240
Or something splashing or sloshing:
http://thejadednetwork.com/sfx/comments/2
Like water:
https://pixta.jp/audio/89981626
Or something jiggling:
https://gist.github.com/UserUnknownFactor/093a2296c5a4d9ef7b404728ebde94a3
In hiragana, it's たぷん (tapun):
https://mainichi-nonbiri.com/onomatopoeia/taputapu/
Sometimes, it's spelled as タプーン/たぷーん (tapūn). The ー elongates the プ (pu).
In manga, タプン (tapun) seems to mainly be used for boobs and flab jiggling, bouncing, swaying, being squeezed, or pressing against something. It's also used for the sound a person's stomach makes when they're eating or drinking something. And when they're full after a meal or a drink. It also refers to just being fat in general, particularly having a flabby belly:
https://ameblo.jp/chi-chanyo777/entry-12833076591.html
A louder, faster variation is ドタプン/ どたぷん (dotapun), or ドタプーン/ どたぷーん (dotapūn), although it seems to mainly refer to gigantic female boobs.
Since I doubt it was inspired by any place called "Punta", I'm gonna conclude that it's a pun of the "tapun" onomatopoeia. I guess it's a reference to the character being a fatass, how his body jiggles when he moves?
Also, note that Japanese onomatopeia is often said twice or multiple times at once (doki doki, muchi muchi, puri puri, dokkan dokkan, etc), too. You can see "Punta" in タプンタプン (ta
puntapun).
So, yeah, I can buy that the character's name is a pun of タプン/たぷん (tapun) or タプーン/たぷーん (tapūn); it basically means "jiggle" and "fat". Although that "DB Mania" fansite was just making guesses, I'd say they were pretty much right on the money. I don't think it's any coincidence at all that a fat character in a Japanese series was given a name that's similar to Japanese onomatopeia for fat people. If there was any meaning behind his name at all, it was probably this.
Oh, there's also the onomatopeia プンタタ (puntata), which is used for music:
http://thejadednetwork.com/sfx/browse/puntata/
Perhaps the character's name is a pun on that and his quick movement could be compared to music beats? Or how quickly Krillin beat his ass? Or perhaps all his flab bouncing around would sound like music? Probably a reach lol
tl;dr his name is a pun on him being a fat fuck