Here are the theories I’m seeing:
1. The Elders are referring to the devil fruit eaten by Zunesha
• Zunesha’s appearance this chapter suggests the fruit is connected to him somehow.
• We know awakened zoan fruits provide monstrous new forms, per Impel Down.
• We know Zunesha is also very old, explaining the fruit’s disappearance for so long.
• Zunesha is tied to the world’s history and has unaddressed lore, which this could explore.
• We don’t know this hypothetical fruit’s name, but various mythical elephants have been suggested (since the default Elephant Elephant Fruit was already eaten by a sword).
2.The Elders are referring to the Gum Gum Fruit/Gomu Gomu no Mi
• We recently learned that the Gum Gum Fruit was guarded carefully by the World Government, suggesting that it’s of interest to them and of greater significance than we know.• Luffy has notably not awakened his devil fruit despite many of his peers and enemies having done so, harkening to the Elder Stars’ comment about awakening.
• The Gum Gum Fruit/Gomu Gomu no Mi’s name could be the false name if Luffy is made of something other than rubber.
• The significance this would have to Zunesha is unclear, but some have suggested that Zunesha is a red herring or that the fruit’s significance to him is yet to be seen.
3.The Elders are referring to the Millet Millet Fruit/Kibi Kibi no Mi
• This fruit has the power to control animals, so it is possible that Zunesha is one of those such animals.• We know Zunesha was sentenced to march the ocean as punishment for a crime; the Millet Millet Fruit would have the power to do this.
• Tama’s powers have been on full display in the raid with CP0 taking note, so it would be reasonable for the Elders to be discussing this now.
• The cryptic/creepy nature of Zunesha suggests an additional effect of the Millet Millet Fruit, one that could be explained through an “awakening” that the Elders mentioned.
• Kibi/Millet is an obtuse enough description of the fruit for it to be a false name.
4.The Elders are referring to the Flower Flower Fruit/Hana Hana no Mi
• The Elders were discussing Robin immediately before mentioning the fruit.• Robin’s powers are not clearly defined and could have a deeper meaning, especially if it’s “awakening” is siginficant.
• The Hana Hana no Mi’s name, bloom and/or flower, is a rather poetic way of describing the fruit’s power and could easily be a false name.
• Like the Gum Gum Fruit, it’s significance to Zunesha is unclear but could theoretically be explained.
5.The Elders are referring to the Time Time Fruit/Toki Toki no Mi
• We already know this fruit disappeared for centuries when Toki jumped forward in time, explaining why “that” fruit has been missing for so long.• The fruit is directly tied to the world’s history, having existed around the time of the Void Century and indirectly tying it to Zunesha (himself having similar significance).
• The fruit and its user share a name, which give credence to the idea that the fruit’s name was changed at some point.
6.The Elders are referring to the Ope Ope Fruit/Ope Ope no Mi
• This fruit has already been foreshadowed to be of greater significance, specifically being known as the “Ultimate Devil Fruit” and its ability to grant eternal youth/immortality at the cost of the user’s life.• Zunesha’s age and appearance suggests that he himself could have been granted that immortality a long time ago.
• The fruit’s name has little to do with it’s literal abilities, meaning it could be a false name.
• Law recently used the fruit’s awakened power in Wano, meaning that CP0 may have seen it and explaining the Elders’ comments on the fruit “awakening”.
7.The Elders are referring to Kaido’s Fish Fish Fruit/Uo Uo no Mi
• Momonosuke’s attempts to stop Onigashima from crashing could be the shadow the agents are referring to instead of Zunesha, with Zunesha being a red herring.• The fruit is known to be of interest to the World Government; they even attempted to recreate it.
• We have not seen the fruit’s awakening, which could account for it not having “awakened” in so long.
• The fruit’s name could be seen as misleading or silly, which would be explained if it had indeed be renamed by the government.