Warning! Spoilers ahead for Doron Dororon chapter 8!
The meaning behind the title Doron Dororon was revealed in a very subtle way, and it is horrifying. The title is the sound that is emitted when a monster - or mononoke - forces giant claws to rip out from its normal-sized fists in a terrifying bloody display. This meaning is reinforced when the mononoke later perishes.
Mangaka have been notorious for giving their series rather absurd names. But the best ones are those that appear completely random at first but actually aren't. For example, Shonen Jump's PPPPPP is actually named after a rare dynamic marking in music called pianissississississimo, which denotes an extremely soft style of playing. The title fits because the protagonist Lucky used to only play piano for his sick mother at the hospital, and because visitors can't be loud during visitation, Lucky had to play very quietly. And Doron Dororon mangaka Gen Oosuka is following suit with this tradition, just in a more random way.
In choosing to call his series Doron Dororon, mangaka Gen Oosuka basically chose to call his series "Ka-Pow!" or "Boom!", except with his own spin. "Doron Dororon" is Oosuka's own personal onomatopoeia that his mononoke make whenever they unleash a strong attack or emit a powerful aura. The sound can also be heard as their supernatural energy fizzles out upon their death. The latest example of this transpires in chapter 8 with the emergence of a mononoke that is not only responsible for a cataclysmic event known as the Great Disaster, but that kills the hero Dora's mother.
In Doron Dororon, Dora becomes so overcome with the need to seek vengeance on the Great Disaster monster that his mononoke partner Kusanagi actually refuses to let him fight, in what is clearly the most emotional moment in Doron Dororon thus far. But Dora eventually realizes his mistake, and the two team up with their samurai friend Ginchiyo Yagyu to defeat the rampaging opponent. And as the battle unfolds in chapter 8, the creature makes a "Doron" sound right as it's about to shoot a barrage of paralyzing needles and then radiates an intense supernatural energy right after the heroes hear "Dororon" emitting from somewhere deep within the mononoke.
Luckily, readers are expected to find out soon whether the killer of Dora's mother will make the same sounds as other mononoke have when they die, which normally consist of many "Dorons" strung together. Because the manga is called Doron Dororon, it's unlikely that Dora will spend the entire manga trying to hunt down the one monster that killed his mother since every mononoke makes the sound "Doron Dororon." It's possible he will have his vengeance and then go on to achieve his dream of becoming a samurai that slays mononoke, opening up the possibility that he will hear a lot more monsters make the sound, "Doron Dororon."